Uhh... so i'm driving home doing about 40 in 5th in down pouring rain, and all of a sudden my DTC starts spitting out information.

"Shocks Inoporative" "Service Vehicle Soon" "Reduced Engine Power" "Tire Pressure Low" "Service ABS/TCS" etc... then the ABS, Check Gauges, TCS lights all come on (No CEL though...) And the Radio's display is gone, radio gone.

The car however, ran the rest of the way home w/o problems. (Except the No Comm. and idiot lights all on w/ "Reduced Engine power" ) Idles fine, and seems to run fine - although i didn't get on it hard... But after parking it and shutting it down, i noticed my Key Fob doesn't work anymore, and the LED's behind the Heat/AC controls won't turn off...

When i check for codes, i get "No Comm." from EVERY SINGLE module in the DTC's list!

I started it again, and the situation is the same - all the above warning messages, and still "No Comm." with all the control modules.

What does that mean? Where should i check first?


Thanks
Dan

 

Oh - it gets better...

So 15 minutes after I parked it, i'm sitting in my apartment reading about "Reduced Engine Power" when all of a sudden my car alarm starts going off!! I run outside, and my car's freaking out! Lights, Horn, etc! So i hop in (Doors were unlocked even though i manually locked 'em) and turn the key to "On". Then the car shuts up, and the DTC spits out normal info.

No more "Reduced Engine Power" or "Service Vehicle Soon"... the radio, and lights all seem to work normally... Back to normal it seems... but now what do the codes show? Sure enough the 'No Comm.' message was gone and here's the new data.

I checked the codes... there were tons...

There Were:

PCM
P1571H
P1626H
P1644HC
P1652C

TCS
C1281H

BCM
B0844H
U1255H
U1096H
U1016H
U1040H

IPC
U1255H
U1016H
U1064H
U1040H
U1176H
U1176H
U1056H
U1160H

Radio
U1064H
U1016H

HVAC
U1064H
U1096H
U1160H
U1255H

LDCM
U1255H
U1064H
U1016H
U1096H

RDCM
U1255H
U1064H
U1016H
U1096H

RFA
U1255H
U1096H
U1064H
U1016H

A lot of them look redundant... I'm going to start looking them up... At this point, the problem is screaming "Grounding Issue" to me. Anyone else have input?


Thanks
Dan

 

That's a good place to start as it sounds electrical to have that many diverse issues all the sudden pop up out of nowhere. Have the battery checked and especially look for any leakage onto the PCM beneath it.

These cars will do all sorts of whack chit when voltage starts dipping or acid gets on the PCMs connectors etc.

Just another .02

 

The symptoms are so dramatic that it has to be something basic. As Cajun99 says, check for leaks. It'll be obvious if you look around the base of the battery. If you have a leak you'll need a bit of advice on what to check. The wiring to the computer modules is under the tray and can cause major problems if damaged by acid.

If there are no leaks, the first thing to do is to disconnect the terminals, clean them up and reconnect them nice and tight. Next is to have the battery checked if its still happening. I see you have a 97. If its an older battery or, worse still, the original AC Delco, get it changed as a precaution. If a 97 vintage battery hasn't failed yet it will soon; probably dramatically.

There have been many examples on the Forum of random electrical faults caused by bad batteries. The faults are often totally unrelated.

If that doesn't fix it I suspect grounds may be the next to check. There are a couple of electrical gurus here including Bill Curlee who will undoubtedly help out.

 

I've got a 8 month old Optima Red Top. The engine seems to normally operate producing 13.2-13.7 volts depending on how much stuff is running... But i've seen it dip into the mid 12s when applying brakes, or something else. Whats normal for a C5? (My Old man's silverado makes about 14.5 volts at idle...)

The previous battery did leak, and i'm sure some of it got on the PCM, what is the best way to go about removing/cleaning the PCM or is it toast. If so, how do i go about replacing it?

When i bought the car the first thing i checked was the battery. Sure enough it was a leaky crummy battery... so i replaced it with an Optima Red Top... I pulled out the tray and sprayed the foaming color indicating acid neutralizer all over, and rinsed and repeated a couple times... Is there further cleaning i should try?


Dan

 

Weren't you just telling me about a water leak that you were investigating? Or was that in the back........

Not that I have run into that particular problem, but it does sound like a water intrusion or bad connection problem.

Looking at your codes there were only two that were current, would be a good place to begin the troubleshooting-
P1644 Traction Control Delivered Torque Output Circuit
P1652 Powertrain Induced Chassis Pitch Output Circuit
Too bad I don't know WTF either of them means..

If you want a warm dry place to work on it let me know!

 

my car started doing the same thing tonight. all crazy. I can shut off the engine, count to 10, and start her with no problems. THen a few minutes later.. all hell breaks loose.

I feel its a connector issue with the PCM. Ill invistagete tomorrow morning.

chad

 

So... I found atleast one problem...

When i opened the hatch, both the rear left and rear right compartments were full to the brim with water. Completely submerging the RDT (Ride control Module). Carpet was already removed because i was trying to diagnose a leak - i didn't realise it had got so full - it was raining a ton...

Either way, i disconnected that module, and then all the other modules worked again. Once i let it dry all day and reconnected it everything worked again for about 10-15 minutes, then the RDT lost comm. and the shocks don't work. Looks like that module might be toast. But everything else seems to work ok.

Also, i removed both 1/4 panels and used a sealant over the seam along the length of the hatch. Hopefully that'll keep out any more water intrusions...

Any ideas on price of replacing/rebuilding the RDT?

Thanks

Dan

 

So i took off the 1/4 panel and ran silicon sealant down the seem from tail light to b-pillar. I gooped a healthy amount up near the pillar and really applied it generously...



Even with the sealant on the outside, somehow water is still leaking quite freely from above the compartments. (You can see the trail...) Also, the water is still leeking from above the Tire Wells. I seeled around the tire well once, but thats not where the leak is... it's coming in from behind the speaker. Any pictures or tips on getting those plastic speaker covers off would be VERY handy...



I'm going to try and remove the speakers & covers and seal the inside too... hopefully that'll stop the leak...

I notice that the locations around the screws for the 1/4 panel were very wet... (you can see in the pic) is it possible water is getting in there, and working its way to the back, then leaking into the compartment?

All the help is very much appreciated. This leak is no doubt the major cause of my electrical problems... The RTD module i have intermittently works now, and i'm going to take it to work and repair on of the solder connections. (A chip looks corroded and fixing it may help) Does anyone rebuild these, or sell them used or something? I really don't want to spend $700 for a new one from Fred Beans.

Thanks

Dan