'94 Beretta Z26 trans problem
'94 Beretta Z26 trans problem
Hello all, occasional reader, first time poster.
I have a 1994 Beretta Z26, 3.1L V6, 4T60-E auto, 129000 miles. It was stored(though occasionally started and moved around) after previous owner died. I was told it only needed an intake gasket, figured I better start it up and verify this before I dove into the project, turns out the engine had a spun rod bearing.
I bought a 1997 Olds Cutlass Supreme with a rusted frame as a parts donor. I drove the car about 20 miles home, so I know everything functioned properly on the engine and trans. Coolant temp sensor setup was different, as was the rear exhaust manifold and engine motormount, but otherwise it bolted right in. Got it running, time for a test drive...bad news...trans shifted 1,2,4...no 3rd and no TCC lockup. After a few miles of cruising dirt roads, it downshifted to 2nd gear(computer was looking for 3rd, but that didn't work, so ended up in 2nd). Basically, after it warms up, the computer shuts off 4th gear. Since there is no 3rd gear, it went to 2nd. Park it for a couple hours, or till the next day...try it again...same thing. On cold start it shifts 1,2,4...all firm, no slippage, but no 3rd and no TCC lockup. After a few miles, it downshifts and won't go back to 4th till after it cools off.
I had saved the engine compartment wiring harness out of the parts car. I cut the trans connector off and added some solderless T connectors. I plugged this connector into the trans, from one side of the T I plugged into the trans connector on the Beretta's wiring harness. From the other leg of the T I ran wires into the car so I could check the ground circuits while driving. When the post-warmup downshift occurs, the computer is shutting off the ground circuit to shift solenoid A. I thought maybe it was the trans temp sensor, so I hit it with the multimeter, resistance readings were 12530 Ohms cold and about 800 Ohms hot. From what info I've found, this is within acceptable range.
Anyway, 3rd gear was still gone, so I pulled the trans and installed the one that came in the '97 parts car. All plugs, wiring and connections matched. I removed the side cover from the valve body to verify that wiring, solenoids, etc. were the same. I did change the differential, as the reluctor ring on the '97 trans had a 30 tooth count and the reluctor ring on the original '94 trans was a 29 tooth count. Got it all back together, new filter and fluid also, time for a test drive! Shifted 1,2,3,4, TCC lockup perfectly! Fantastic! But...only went a couple miles and it downshifts to 3rd gear again. Park it for a while, cold startup, everything works great. A few miles down the road and you're back to 3rd, won't go to 4th till it sits for a while. Same thing every time. Grrr!!!
I found a great technical paper that listed all the sensors that the computer reads to calculate shifting. It lists Coolant Temp Sensor, TPS, VSS, Vacuum Sensor, Park/Neutral switch, Temperature Sensor and Engine Speed sensor as inputs.
I have changed the Coolant Temp sensor and TPS with known good used ones. Vacuum Sensor I assume refers to the MAP sensor? Changed that today, didn't make any difference.
VSS I haven't checked or changed, speedometer works smoothly so I'm guessing there isn't a problem with that.
Park/Neutral switch I haven't checked or changed, but it does only start in P or N, backup lights come in on R, etc. so I'm guessing there isn't a problem there. I did read somewhere in researching this problem that it could be caused by a bad Range Switch? I haven't been able to locate a pinout and testing procedure for this yet.
Trans Temp Sensor I haven't checked or changed, as it worked flawlessly before I removed it from the parts car.
Engine Speed sensor I assume refers to the cam sensor? Tach works fine, so I haven't done anything with that.
Of course, my assumptions could be completely wrong.
Sevice Engine Soon light is not on. But...that doesn't necessarily mean there isn't a trans code stored because of mechanical failure in previous transmission?
ABS light is on. Wires to wheel sensor were broken on right lower control arm. Repaired the break but ABS light still on. But I don't think this would cause the shifting problem?
I was going to try jumping the A and B terminals in the OBD I connector, but there's no wire in the B hole. Can this be checked without using a scanner? It's a 12 pin connector, not a 16 pin. I don't have plates or insurance on it, as I wanted to make all repairs first, so I can't really run it to town for a scan.
So, in summation, it's a '94 Beretta with engine and trans from a '97 Cutlass Supreme, no 4th gear or TCC lockup after driving a few miles. On cold start, everything is great. Seems like the computer is interpreting the signal from the Trans Temp Sensor backwards.
Your opinions and suggestions are appreciated.
Thanks,
Anthony
Located just outside the huge town of Moscow, MI. Don't blink or you'll miss the whole thing.
I have a 1994 Beretta Z26, 3.1L V6, 4T60-E auto, 129000 miles. It was stored(though occasionally started and moved around) after previous owner died. I was told it only needed an intake gasket, figured I better start it up and verify this before I dove into the project, turns out the engine had a spun rod bearing.
I bought a 1997 Olds Cutlass Supreme with a rusted frame as a parts donor. I drove the car about 20 miles home, so I know everything functioned properly on the engine and trans. Coolant temp sensor setup was different, as was the rear exhaust manifold and engine motormount, but otherwise it bolted right in. Got it running, time for a test drive...bad news...trans shifted 1,2,4...no 3rd and no TCC lockup. After a few miles of cruising dirt roads, it downshifted to 2nd gear(computer was looking for 3rd, but that didn't work, so ended up in 2nd). Basically, after it warms up, the computer shuts off 4th gear. Since there is no 3rd gear, it went to 2nd. Park it for a couple hours, or till the next day...try it again...same thing. On cold start it shifts 1,2,4...all firm, no slippage, but no 3rd and no TCC lockup. After a few miles, it downshifts and won't go back to 4th till after it cools off.
I had saved the engine compartment wiring harness out of the parts car. I cut the trans connector off and added some solderless T connectors. I plugged this connector into the trans, from one side of the T I plugged into the trans connector on the Beretta's wiring harness. From the other leg of the T I ran wires into the car so I could check the ground circuits while driving. When the post-warmup downshift occurs, the computer is shutting off the ground circuit to shift solenoid A. I thought maybe it was the trans temp sensor, so I hit it with the multimeter, resistance readings were 12530 Ohms cold and about 800 Ohms hot. From what info I've found, this is within acceptable range.
Anyway, 3rd gear was still gone, so I pulled the trans and installed the one that came in the '97 parts car. All plugs, wiring and connections matched. I removed the side cover from the valve body to verify that wiring, solenoids, etc. were the same. I did change the differential, as the reluctor ring on the '97 trans had a 30 tooth count and the reluctor ring on the original '94 trans was a 29 tooth count. Got it all back together, new filter and fluid also, time for a test drive! Shifted 1,2,3,4, TCC lockup perfectly! Fantastic! But...only went a couple miles and it downshifts to 3rd gear again. Park it for a while, cold startup, everything works great. A few miles down the road and you're back to 3rd, won't go to 4th till it sits for a while. Same thing every time. Grrr!!!
I found a great technical paper that listed all the sensors that the computer reads to calculate shifting. It lists Coolant Temp Sensor, TPS, VSS, Vacuum Sensor, Park/Neutral switch, Temperature Sensor and Engine Speed sensor as inputs.
I have changed the Coolant Temp sensor and TPS with known good used ones. Vacuum Sensor I assume refers to the MAP sensor? Changed that today, didn't make any difference.
VSS I haven't checked or changed, speedometer works smoothly so I'm guessing there isn't a problem with that.
Park/Neutral switch I haven't checked or changed, but it does only start in P or N, backup lights come in on R, etc. so I'm guessing there isn't a problem there. I did read somewhere in researching this problem that it could be caused by a bad Range Switch? I haven't been able to locate a pinout and testing procedure for this yet.
Trans Temp Sensor I haven't checked or changed, as it worked flawlessly before I removed it from the parts car.
Engine Speed sensor I assume refers to the cam sensor? Tach works fine, so I haven't done anything with that.
Of course, my assumptions could be completely wrong.
Sevice Engine Soon light is not on. But...that doesn't necessarily mean there isn't a trans code stored because of mechanical failure in previous transmission?
ABS light is on. Wires to wheel sensor were broken on right lower control arm. Repaired the break but ABS light still on. But I don't think this would cause the shifting problem?
I was going to try jumping the A and B terminals in the OBD I connector, but there's no wire in the B hole. Can this be checked without using a scanner? It's a 12 pin connector, not a 16 pin. I don't have plates or insurance on it, as I wanted to make all repairs first, so I can't really run it to town for a scan.
So, in summation, it's a '94 Beretta with engine and trans from a '97 Cutlass Supreme, no 4th gear or TCC lockup after driving a few miles. On cold start, everything is great. Seems like the computer is interpreting the signal from the Trans Temp Sensor backwards.
Your opinions and suggestions are appreciated.
Thanks,
Anthony
Located just outside the huge town of Moscow, MI. Don't blink or you'll miss the whole thing.
Re: '94 Beretta Z26 trans problem
I had (have?) a '95 Z-26, 3100/4T60E, so I feel some of your pain with this. It sounds like you've done your homework, and know more about the 4T60E than I do, or want to. 
But, let me add the few tidbits I have that might prove helpful, until a more educated or knowledgeable member can jump in. First, '94 is the beginning of GM's transition from OBD1 to OBD2, which didn't really come out until '96, so '94 and '95 are bastard years. You cannot read codes with a jumper wire, but you also cannot plug in an OBD2 scan-tool to access codes. You need special equipment, like a Tech 2 (IIRC) or similar. 
, basically, you are SOL on that.
The ABS light (or system) shouldn't be effecting your shifting.
The 'range' switch is the shift-select switch, and if bad, that could be your cause right there. Odd that it wouldn't misbehave when cold though.
The vacuum modulator (round diaphragm mounted on the front of the transmission) would be my best guess as to your trouble. Also check the vacuum lines to it, and the accumulator for the vacuum system. The vacuum system also operates your heater controls, so consider whether or not your shift problems coincide with using your defroster or heater, and not just if the engine has actually warmed up.
Engine speed sensor most likely refers to the 7X CKP, or the crank sensor on the back of the block -the 24X (hi-res) CKP and CMP (cam sensor) are used more for the SFI function of the fuel control system, and the PCM can function without them. Without the 7X, your car will not run, period.
Hope some of this helps, good luck!
But, let me add the few tidbits I have that might prove helpful, until a more educated or knowledgeable member can jump in. First, '94 is the beginning of GM's transition from OBD1 to OBD2, which didn't really come out until '96, so '94 and '95 are bastard years. You cannot read codes with a jumper wire, but you also cannot plug in an OBD2 scan-tool to access codes. You need special equipment, like a Tech 2 (IIRC) or similar. , basically, you are SOL on that.The ABS light (or system) shouldn't be effecting your shifting.
The 'range' switch is the shift-select switch, and if bad, that could be your cause right there. Odd that it wouldn't misbehave when cold though.
The vacuum modulator (round diaphragm mounted on the front of the transmission) would be my best guess as to your trouble. Also check the vacuum lines to it, and the accumulator for the vacuum system. The vacuum system also operates your heater controls, so consider whether or not your shift problems coincide with using your defroster or heater, and not just if the engine has actually warmed up.
Engine speed sensor most likely refers to the 7X CKP, or the crank sensor on the back of the block -the 24X (hi-res) CKP and CMP (cam sensor) are used more for the SFI function of the fuel control system, and the PCM can function without them. Without the 7X, your car will not run, period.
Hope some of this helps, good luck!
1989 SuperCharged 3800 Srs-II (First)Six-Speed GTU
1990 Turbo 3.4 5-Speed T-Type
1990 4.0L 4-Cam 32-Valve V-8 5-Speed Indy GTi (Project)
1990 Stock(!) 3.1 MPFI Auto Indy
1995 LA1/L82 4T60E Z-26
1995 3.4 DOHC Turbo 5-Speed Z-26
1990 Turbo 3.4 5-Speed T-Type
1990 4.0L 4-Cam 32-Valve V-8 5-Speed Indy GTi (Project)
1990 Stock(!) 3.1 MPFI Auto Indy
1995 LA1/L82 4T60E Z-26
1995 3.4 DOHC Turbo 5-Speed Z-26
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meeksberetta
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Money pit Beretta
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Re: '94 Beretta Z26 trans problem
An OBD1 scanner will read the codes. My AutoXray is OBD1,OBD2 and CAN. It will read engine codes on my 95, but not brake codes. Is there a way that you can rent an OBD1 code scanner anywhere?
If you think that you have solved some or all the problems you can reset the computer. If the check engine light comes back on you have more work to do.
3X00 is the trans expert here and would be the most helpful.
Meeks: the only problem I had was at 150k the trans would take a long time to shift if you pressed the gas any more than normal. My trans has been replaced so that is all I can say.
If you think that you have solved some or all the problems you can reset the computer. If the check engine light comes back on you have more work to do.
3X00 is the trans expert here and would be the most helpful.
Meeks: the only problem I had was at 150k the trans would take a long time to shift if you pressed the gas any more than normal. My trans has been replaced so that is all I can say.
keep'em flying!
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3X00-Modified
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Re: '94 Beretta Z26 trans problem
Only real way to tell whats going on is to get a scan tool hooked up to it and watch the shift solenoids as well as the sensor inputs. The 94-95 cars are typically easier to work with when it comes to trans swaps and don't get too picky... the OBDII stuff on the other hand will throw trans component slip codes and drop out of TCC Lockup only when you swap in a trans with a different final drive ratio. I had a 3.33 in my 95 for a long time and never had any issues... only after I did my OBDII swap did it present the code and start disabling TCC... but never 4th. You may have another issue somewhere that's causing the car to go into limp mode completely hence the reason why this happened before when you were missing 3rd as well... It may have nothing to do with the trans at all and be specific to the engine. But without the scan tool to verify all the sensors are working appropriately then you are always just shooting in the dark and replacing stuff blind. I was never a fan of that and it's why I own an old school Actron OBDI scan tool I got on ebay eons ago... I also have a generic OBDII tool that I can use my laptop with to do almost any other vehicle.
And yes the 94-95 cars are technically OBDI still, the difference is they are Flash proms, Not removable like the 93 and older are, as well as they do not offer a jumper wire to see present codes, they started to intro the flashing option which was going to be new for OBDII but they kept the Diagnostic system at I and did not up it to II.
And yes the 94-95 cars are technically OBDI still, the difference is they are Flash proms, Not removable like the 93 and older are, as well as they do not offer a jumper wire to see present codes, they started to intro the flashing option which was going to be new for OBDII but they kept the Diagnostic system at I and did not up it to II.
Re: '94 Beretta Z26 trans problem
My '95 was problematic for me, as it is an automatic. But it ran and shifted fine, aside from the typical LIMG problem caused by it being a 3100 SFI instead of a 3.1 MPFI.meeksberetta wrote:Is the 95-96 Z26's problematic ?
The only codes it threw at me were almost certainly due to the EGR being removed when I upgraded the intake to a 3400 big-port...1989 SuperCharged 3800 Srs-II (First)Six-Speed GTU
1990 Turbo 3.4 5-Speed T-Type
1990 4.0L 4-Cam 32-Valve V-8 5-Speed Indy GTi (Project)
1990 Stock(!) 3.1 MPFI Auto Indy
1995 LA1/L82 4T60E Z-26
1995 3.4 DOHC Turbo 5-Speed Z-26
1990 Turbo 3.4 5-Speed T-Type
1990 4.0L 4-Cam 32-Valve V-8 5-Speed Indy GTi (Project)
1990 Stock(!) 3.1 MPFI Auto Indy
1995 LA1/L82 4T60E Z-26
1995 3.4 DOHC Turbo 5-Speed Z-26
Re: '94 Beretta Z26 trans problem UPDATE
Got it scanned today, results were Trans Temp Too Cold (110 degrees after driving about 4 miles) and Quad Driver 4 bad. I've done a little internet research but haven't found out yet what Quad Driver 4 pertains to. Am I looking at a PCM replacement?
If the Trans Temp is too low, why does it shift correctly on cold startup? It's not till after you drive 2 - 5 miles that it downshifts to 3rd.
I did finally try out the cruise control; it doesn't work but I haven't done any troubleshooting on that yet either, could be something simple, and an unrelated issue.
I'll do more research tonight, have to get back to wrenching for now.
Thanks,
Anthony
If the Trans Temp is too low, why does it shift correctly on cold startup? It's not till after you drive 2 - 5 miles that it downshifts to 3rd.
I did finally try out the cruise control; it doesn't work but I haven't done any troubleshooting on that yet either, could be something simple, and an unrelated issue.
I'll do more research tonight, have to get back to wrenching for now.
Thanks,
Anthony
Re: '94 Beretta Z26 trans problem UPDATE #2
A little more info: this car has a auxillary trans cooler on it. However, the trans lines are NOT connected to the factory cooler on the radiator tank. If the trans lines were connected to the radiator, the trans temp and coolant temp should be roughly the same, yes? Since the trans lines are are not connected to the radiator, after driving a few miles, the PCM would getting a signal from the coolant temp sensor saying "ok, I'm about 200 degrees" while also getting a signal from the trans temp sensor saying "hey, I'm only 110 degrees!". Could this be confusing the solder out of the PCM, and thus making the PCM think it's too cold to use 4th gear and the TCC?
The radiator has been changed due to deer damage. I'm thinking I'll buy adapters tomorrow so I can hook the trans lines to the radiator and see if that makes any difference.
Your opinions and suggestions are appreciated.
Thanks,
Anthony
The radiator has been changed due to deer damage. I'm thinking I'll buy adapters tomorrow so I can hook the trans lines to the radiator and see if that makes any difference.
Your opinions and suggestions are appreciated.
Thanks,
Anthony
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3X00-Modified
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Re: '94 Beretta Z26 trans problem
The trans lines going through the radiator does two things... Warms the fluid to the proper temp in the time the trans needs to operate properly as well as keeps it around the same temp as the coolant. So yes with this removed you are quite possibly running the trans too cold and because it's not getting to temp it goes into limp mode where it will disable 4th... It's not the physical temp of the fluid causing 4th to stop working its the ECM commanding it to stop because the fluid isn't getting to operating temp so it assumes something is wrong with it.
Re: '94 Beretta Z26 trans problem Update #3
Got the transmission lines connected to the radiator. Made no difference, still downshifts to 3rd gear after a few miles.
Antifreeze and trans fluid are both full. I zapped the steel part of the trans lines near the radiator with a non-contact thermometer, one read 175 degrees, the other read 147 degrees. I hooked up my test harness to the trans and checked the resistance on the trans temp sensor. On the 20K Ohm scale, it read .32; bump the decimal over three places because I'm on the 20K scale and you have 320 Ohms. From what I have been able to find online, GM oil temp sensor resistance at 80 degrees Celsuis(176 degrees F) should be 332.
I'm guessing the trans temp sensor is NOT the problem? Possibly a broken wire/bad connection between trans connector and PCM? Or PCM is misinterpreting the signal that it's getting from the trans? PCM is 16196397.
I still haven't found any info on what the "Quad Driver 4 bad" error pertains to.
Where can I find a pinout for the PCM? I could then check resistance on the trans temp sensor wires at the PCM plug. This would tell me if it's a wiring issue or a PCM issue, yes?
Thanks,
Anthony
Antifreeze and trans fluid are both full. I zapped the steel part of the trans lines near the radiator with a non-contact thermometer, one read 175 degrees, the other read 147 degrees. I hooked up my test harness to the trans and checked the resistance on the trans temp sensor. On the 20K Ohm scale, it read .32; bump the decimal over three places because I'm on the 20K scale and you have 320 Ohms. From what I have been able to find online, GM oil temp sensor resistance at 80 degrees Celsuis(176 degrees F) should be 332.
I'm guessing the trans temp sensor is NOT the problem? Possibly a broken wire/bad connection between trans connector and PCM? Or PCM is misinterpreting the signal that it's getting from the trans? PCM is 16196397.
I still haven't found any info on what the "Quad Driver 4 bad" error pertains to.
Where can I find a pinout for the PCM? I could then check resistance on the trans temp sensor wires at the PCM plug. This would tell me if it's a wiring issue or a PCM issue, yes?
Thanks,
Anthony
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3X00-Modified
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Re: '94 Beretta Z26 trans problem
Might be easier to swap out the ECM for another 94 or 95 one to see if that quad driver error goes away. Also if you had a way to pull codes does that device also read data? That may help you understand what info it's not getting back from the trans.
Re: '94 Beretta Z26 trans problem Update #4
Spent $40 on a used computer from a local salvage yard. Car will crank and fire up for a second but won't stay running. Figured it was a bad PCM, so I went back and swapped it for another one. Same thing: crank and fire, crank and fire, crank and fire but won't run. Dang it. Do I have to get it flashed or something? I expected that, if it came out of another running vehicle with the same engine/trans, I'd be able to plug it in and go. Am I wrong? Good thing I kept my original PCM and used a different one for the core. All the PCMs are 16196397 but the four letter extension is different. Of what significance is the four letter extension? Where can I look it up to find out what vehicle the PCM came out of and what will interchange?
Wiring for trans temp sensor from trans case connector to plug on PCM appears to be fine. It shows continuity, so there's no break in the wiring. 5V lead, on cold startup, reads just under 5V. When vehicle is up to operating temp, the lowest it reads is 2.12V. But then it comes back up to about 3.5V and locks out 4th gear. I'm guessing this is faulty operation of the trans temp sensor, and it's not grounding out the 5V line correctly? Or is the trans temp sensor working correctly, and the PCM is applying incorrect voltage to the circuit? Grrr... I haven't been able to get it back on the scanner yet. But I did find a local shop that will do it for $10, so should be easier to get that done now.
I opened up the wiring harness loom by the heater fan motor and located the 5V feed and ground wires that go to the trans temp sensor. I'm seriously considering cutting these two wires, connecting them with a 300 Ohm resistor and see what will happen. According to info I've found, trans temp sensor should have about 300 Ohms resistance when approximately 180 degrees. I'd have to put my original PCM back in so the car will actually run, but that will only take a minute to do.
It's cold and nasty outside but maybe, after ex picks up the kids, I can get back out there and do more. Will post results.
Merry Christmas to all!
Anthony
Wiring for trans temp sensor from trans case connector to plug on PCM appears to be fine. It shows continuity, so there's no break in the wiring. 5V lead, on cold startup, reads just under 5V. When vehicle is up to operating temp, the lowest it reads is 2.12V. But then it comes back up to about 3.5V and locks out 4th gear. I'm guessing this is faulty operation of the trans temp sensor, and it's not grounding out the 5V line correctly? Or is the trans temp sensor working correctly, and the PCM is applying incorrect voltage to the circuit? Grrr... I haven't been able to get it back on the scanner yet. But I did find a local shop that will do it for $10, so should be easier to get that done now.
I opened up the wiring harness loom by the heater fan motor and located the 5V feed and ground wires that go to the trans temp sensor. I'm seriously considering cutting these two wires, connecting them with a 300 Ohm resistor and see what will happen. According to info I've found, trans temp sensor should have about 300 Ohms resistance when approximately 180 degrees. I'd have to put my original PCM back in so the car will actually run, but that will only take a minute to do.
It's cold and nasty outside but maybe, after ex picks up the kids, I can get back out there and do more. Will post results.
Merry Christmas to all!
Anthony
Re: '94 Beretta Z26 trans problem Update #5
I think I finally got it. I located the trans temp wires in the wiring harness by the heater fan motor. I cut the wires and connected them with a 270 Ohm resistor. This resistor value should tell the PCM that the trans is running about 185 degrees. I have driven it twice and it has worked flawlessly both times. Apparently the trans temp sensor is failing intermittently; I had checked it a couple times and it was within the correct resistance range, but it seems to not be giving a steady signal to the PCM.
Hopefully my little adventure and it's associated info will be of use to others as well.
Thanks,
Anthony
Hopefully my little adventure and it's associated info will be of use to others as well.
Thanks,
Anthony