REALLY the Knock Sensor or is it the ECM?

[SuzukiGhostRider]

So, the car:

'92 Beretta GTZ with Quad 4/5 speed.

The issue:

Throwing two codes upon startup today after several days of NOT driving it. No codes when last parked.

1. Code 66: A/C pressure sensor - Circuit problems or low A/C charge OR ECM computer circuit problem - Internal reset occured.

2. Code 43: EST circuit - low voltage detected OR ESC - Circuit problems.

Now here's the rub:

I have been driving this car since February and not once have I gotten the knock sensor code (code 43). But, I've not driven the GTZ in several days and it's been raining here non-stop almost for 3 days and nights. I noticed night before last when checking on the cars (I decided to look in the GTZ passenger window to make sure I didn't have the infamous leak) that the Quasar was dripping water center mast of the glove box onto the floor mat. Now, I've checked this car many times ,including when I first got it, to make sure it didn't have this issue. Never showed up , but we've never had THIS much rain.

It was a slow drip , once every few seconds one drop at a time.

I got a towel and put it down on the floor. Not much else to do at the time. Was 2 am.

Also, this car has had a "stumbling start" issue since I got it. ONLY when cold, and ONLY the first start of the day. I've always kind of written it off as a fuel pressure check ball problem. But, the thought crossed my mind that this can also be caused by a weak ECM.

Even after the rebuild it still does it.

Now , with the presence of these codes, and the water that leaked into my passenger cabin the last few days, I'm thinking some moisture got into/on the ECM and finished it off.

The car seems to run fine, but kicks the CEL after a few minutes and the fan EVERY time. I may go ahead and do an KS just to be sure, but I'm leaning to the ECM being shot.

Opinions? Advice?

Thanks.

[pghturbo88]

I had posted some extensive experiences from my dealings with intermittent knock sensor codes on my 89 2.8L on the "other" Beretta forum, but they are now gone. Long story short, I learned that the knock sensor circuit resides on the MEMCAL, and it took a combination of a NOS MEMCAL and a JY ECM to make my problems go away. As for your situation, SGR, before replacing anything, I'd first pull the ECM pig tail connectors and check for corrosion and / or moisture. A can of quality electronic spray cleaner (that leaves no residue) will be your friend here. I used a paper clip to "clean" the pigtails in combination with the electronic spray cleaner. You may also wish to remove and re-seat the MEMCAL. Also clean the ECM pins (I used a nail file and the spray). Inspect the interior of the ECM to make sure there is not residue across the circuit board. With all of the circuitry clean and dry, I'd try it again. If you still get a CEL, you may have to replace the ECM and/or MEMCAL; ECM's readily available at a JY, MEMCAL's more challenging to find. I did read the knock sensor circuit ohmic value from the ECM pigtail, and it was within service manual specs, so I knew my field wiring was good. GL, SGR!

http://www.crcindustries.com/hd/content ... =05103&S=N

[scd88ga]

Replacing my ecm and memcal did the trick for me when I first rebuilt my car and got it running 11,000 miles ago. It was causing an array of odd things such as bogus CEL's, fan turning on and off with the cel, and erratic idle! Upon inspection of my ecm and memcal, I had no corrosion or water damage that could be seen. I ended up putting in a matching ecm and memcal from a salvage yard 94 quad Z26, so I never really found out which of the 2 parts was the culprit. I have a couple known good used ECM's here, but I'm unsure if they will work for your car off hand. Also, as I'm sure you already know is you can use any obd1 quad memcal and just have it burned for your car by Jeff (racin17).

[SuzukiGhostRider]

Been a very busy weekend for me work wise. Finished a rebuild on an engine in a customer's suv and did a few other things. So , unfortunately, no time to grab the ECM outta the Quasar yet.

[woody90gtz]

I think the quad is just a regular 7730 ECM, which should be easy to find. The stock memcal would be the tough one to find, so a new burned one would probably be the way to go.

[3400beretta]

^ Nope. '707 ecm up to 92 I believe.

[scd88ga]

I have two good working 707's available (from a 19,000 mile LD2 Auto 1991 Calais and a 84,000 mile LD2 Auto 1991 Grand Am) Both come with the EPROMS that can be used as a core to burn for his application.



I'm unsure if these are the correct ECM's, because I was lazy and didn't look it up before posting.

[SuzukiGhostRider]

I have access to the correct E-prom. Thanks for the offer though.

I still didn't get the ECM pulled (been busy and had to deal with REAL pita customer today) , but I did get a chance to start it and let it idle for about 15 minutes. No codes, no fan on, all good.

Car fixed itself! Wish more would do that, lol. J/K, I know it's not REALLY fixed, but this just confirms my suspicions. We've had a few "indian summer" days here and it apparently got warm enough to dry the ECM out. I drove it 50 miles tonight round trip with zero issue.

So, apparently, I need to get the leak fixed asap. I know where to look.....

[DTMAce]

I hate it when that happens. I had a similar problem a while back, it was stumbling, running rich, but no codes. Then it stopped doing that. Been fine now for awhile. I swear, the more electronics they give these cars, the more easily they can get goofy when they are old. Can you imagine what some of these late model vehicles will be like when their computers start doing weird crap due to corrosion, bad wire, etc?

lol

[3X00-Modified]

They smartened up with the newer ECM's and made them pretty much waterproof.

[SuzukiGhostRider]

So, went to town today and the light came on just leaving the driveway. Then off for a bit on the interstate and back on. It went back off when I downshifted to 4th and went around someone. Stayed off for a bit, came back on. Then off again when I compression braked coming off of the interstate.

Soooooo.... That's REALLY got me thinking KS again, as downshifting would change engine vibration, and we all know Quads are quite fond of NVH. So, I had a KS for the Quasar put aside at the parts store with my name on it. I should get a chance to get it done today. Then we'll see where we stand and whether or not I still need to pull the ECM. I probably should anyhow, just to air on the side of caution.

Can you believe the damn KS is gonna run me $40??

[3X00-Modified]

Can you believe the damn KS is gonna run me $40??

duhhh it's a Quartz Crystal.... lol

[SuzukiGhostRider]

Well it turns out it really IS the ECM. Or has to be anyway......

Put a brand new knock sensor in today and she still threw both codes.

Pulled the ECM and guess what? It appears FINE. No corrosion on the pins or wire harness plugs at ALL anywhere. They were all in PERFECT condition.

I couldn't see any burnt spots on the ECM or chips or what have you. The coating seems perfectly intact on the board. I sprayed the ECM , E-PROM connector and cover out while dis-assembled just cause anyhow. Reassembled and put it back in. Same story.

I cleared all codes, started car and it threw both codes again shortly thereafter.

I then took note of what I presume to be the BCM and guess where IT resides? DIRECTLY under the fresh air vent and behind the glove box, which seems to be the source of my leak. And IT has DEFINITELY gotten wet in the past. You could see the stains on the outer case. So I pulled IT and pulled it apart. INSIDE seems perfectly fine as well. Body harness connectors and pins on the BCM again, were perfect. Gold plated on this one even. Sprayed it out just cause,put it back together ,reinstalled, and restarted car again.

Same story. Short time later BOTH codes came back again.

So, I said gently caress it. I had the parts store order me a reman ECM. Btw, my ECM is a 6450 which is exactly what the parts store listed for this year and model of Beretta.

Pics below. Top 3 are the ECM, bottom pic is the BCM.

[3X00-Modified]

That second box is the air bag module if I'm not mistaken.

[DTMAce]

Yep. Air bag ECM. Pulled one just like it out of the red base. Yellow plugs usually are for ABS stuff. Notice I said usually. hah