I have, I actually troubleshot an issue in there a few months back. That error seems to manifest itself as a NO COMM situation (at least it did in my case, and in my searches at that time). I suppose it couldn't hurt to pull out the accordion tubes and disconnect the wires in there and see if anything changes.

I would say I'd try that tomorrow, but this is the first weekend that my wife and I have had off together in forever, and she's forbid me from working on the car both days. So, maybe I can steal out there to try it...but only maybe.

 

Water under the driver's seat therefore wet carpet? I can't imagine that you have all that happening at yet no codes being present. Assuming you are pulling the codes correctly via the DIC and checking all systems, I think its time for using a Tech2 and I'm sorry to say, a trip to the dealer if you don't have access to a Tech2. I would call around to the various dealers first and ask the questions if they have someone who knows Corvettes and diagnosiing issues. I'm tempted to venture a guess that since the oil temperature is still messed up, there should be a code in there and its possible the wiring issues you found and repaired, could have cooked the PCM itself which means a trip to the dealer anyway.

 

Find the two serial data STAR connectors in the passengers foot well. There to the left of the BCM. They are small thin connectors. The one that has FOUR wires is the one that has the data wires for both doors and the seat control module. Unplug the top of that connector and that willl take all those modules out of the equasion. If you disconnect the other one, the engine will not run because the BCM and PCM cant talk.

See if you still have the issue with the doors and seat out of the circuit.

BC

 

Does anyone know what is common to all of these problems I'm having? Does the coolant temp and oil temp get routed thru the PCM, so if it's fried it'll give bad values to the cluster? Is there any place at all where coolant temp and oil temp share a commonality?

 

They both feed the PCM and the coolant temp is the critical of the two.

 

Bill, I'm not having any serial bus problems. What would be the reasoning behind this troubleshooting?

 

He suggested that to eliminate the other modules that could be involved. Its like removing %50 out of the overall equation.

 

The reason that I asked you to look at the serial buss is that you most likely have a serial buss issue. The coolant. fuel and oil pressure gages are commonly connected to the PCM VIA one wire on the class 2 serial buss. They are NOT connected to the sensor directly. There imulated gages.



If you disconnect the three modules from the other modules, you eliminate them from the issue and can concentrate on other areas.


The three modules that you disconnect are the most common cause of serial data line corruption.

Bill

 

Alright, I haven't had any time to work on the car in the past couple of days, but I will be pulling the door accordions apart tonight to disconnect both electrical connections in each door, AND for good measure I'll pull off the smaller star connector. I can't decide if I should wait until I see the symptoms and then pull the connections to remove the doors and seats, to see if the problems go away, or if I should pull the connections first and see if the problems don't recur. Troubleshooting conundrum.

Also, just for my information, a replacement PCM has to be programmed with my VIN, correct? This requires a Tech 2 or EFI Live, I believe. I have been quoted $115-$150 to reprogram from local shops and dealers, as they say they have to re-flash the whole PCM to edit the VIN. I have a line on a used PCM from an '03 Z06, but if it costs as much just to flash that PCM with my VIN as it costs for a reman w/ my VIN, then it doesn't seem like used is the way to go.

Will the car run with a PCM that isn't programmed for my VIN? I'm assuming I'd need an LS1 PCM, and not a 411 PCM but from a 4.3 V6 or something, but I just want to know if it'll run and if so, what the disadvantage is of not having it programmed for the appropriate VIN.

Thanks guys.

 

If you go to replace the PCM, it needs RPO codes, security and so on, all programmed into it. This requires a Tech2 to accomplish. No, you cannot put it in and drive to the dealer unless you accomplish a security relearn procedure first. If it can't talk to the BCM because the hidden security password doesn't match between the BCM and PCM, the car will not start...therefore the security relearn procedure.

 

Are the prices I was quoted reasonable to have this programming done?

 

If they are going to install it and program it, I say its a fair price. Are you sure yet that its bad or just throwing money at it in a hope?

 

That was a price just for programming on a bench in one shops case, the dealer said I would have to have it installed in the vehicle for them to program it.

I finally got the car to throw a code: PCM P1115H, coolant temp sensor intermittent high voltage. It's somethingg, though. I had some U1016 codes after I took the doors out of the loop.

Speaking of, I am sitting in the car right now with the doors disconnected and the star connector for the doors/seats disconnected, and problems remain. Very sad.

I am not 100% sure the PCM is at fault, but I was reading in another thread where Bill posted PCM info from the service manual, and it stated that a short to ground cold be highly detrimental to the PCM. It also stated you need a meter with >10kohm input impedance to measure voltages from the PCM, so after I post this message I am going to grab my Fluke from my work truck (which fits that bill) and test the voltage to and from the ECT.

Wish me luck.

 

Disconnect the connector from the coolant temp sensor and read the 5 VDC side to ground with the ignition switch to ON (engine OFF). The brown wore should be the 5 VDC side. The yellow wire is the signal wire. Make sure that the connector is not damaged and the wires are not shorted or loose. They can be easily broken at the back of the connector.

If its good, the problem could be related to shorted wires in the engine wiring harness. Theres a common point that this happens. Look on the drivers side of the engine and you will see where the harness run along side the intake manifold. Where it goes down the back of the engine it bends around the bracket on the back of the manifold. Look for pinched/abraded wires at that point:






BC

 

I have 5.02 volts on the sensor connector; try as I might I couldn't manage to fit a jumper from that 5v line AND a multimeter lead inside the connector to actually read the output voltage.

I just went to take a look at the area you just pointed out Bill; my BBK intake manifold doesn't have that bracket so the wire isn't pinched there at all. I moved the harness around a bunch and tried massaging the wires inside the harness while a buddy watched the gauges; nothing made a difference. I checked on the passenger side as well, pulled the battery and inspected the harness underneath (again), and triple verified the grounds behind the headlights. Does anyone know exactly where the PCM gets its ground from so I can be certain I've checked it?

I'm really starting to think my PCM is gone. Ugh.

 

Check G-104/108 at the battery /frame ground :



&


G-106 Battery neg cable ground on the engine block.

BC

 

Checked both (engine ground while under car when I fixed the melted wires, ground beneath battery a few minutes ago), both are clean as a whistle and show no resistance to the battery negative terminal.

 

WHAT DOES THE "Coolant Temp Sender connector and wiring harness / connector and wiring look like?? Pictures please....

Bill

 

Ask and ye shall receive...





I just spent the last couple of hours going over as much of the harness as I was able to lay my hands on, above and below the car; I pulled the ECT and oil temp wires together and individually, and massaged the harness to see if I could get the symptoms to vary in any way, while a helper sat in the car and watched gauges and such. I removed the wheel well access to the PCM and massaged the wires in there, and disconnected/reconnected the PCM connectors to see if I could make a difference. I also pulled, re-cleaned, and reconnected the drivers and passengers side engine grounds and that ground under the battery that Bill posted a pic of (G104). Nothing made a difference (you can imagine it was a frustrating couple of hours).

 

Looking at that ECT connector in that picture I noticed it looked dirty/greasy; I sprayed the wires and the ECT sensor itself with electrical contact cleaner and am letting it dry. I doubt it'll make any difference, but we'll see.

As it is, I think I'm going to order a replacement PCM tomorrow...I can't find any other smoking gun.