I have looked at many threads on electrical issues, but hoping for some pointers in the right direction from the electrical experts here. Car is a 2002 Z06 with only 16K miles (garage queen all its life). Anyway, took it to the track last weekend and went to make an 1/8 mile pass. At the top of 2nd gear around 6000 rpm's the car closed the throttle and nosed over... It was still idling but wouldn't let me give it any throttle. I idled my way back to the pits and was able to give it some light throttle to get there. Shut it off, checked the datalog and everything looked fine (looked as if I just let off the gas at 6000 rpm's). Fired the car back up thinking it was a fluke and tried again. This time, it acted up in the burnout box... same thing, closed the throttle on me. So I left there and tried to limp it back home. Stalled twice on me going up a hill at 15 mph. Each time it would fire back up but it was not happy with me trying to give it much throttle at all. Here are the codes I've got in the DIC, and I have cleared them several times and ran the car to see which ones came back:

TCS C1232 (this one was present before the erratic behavior started so it may be unrelated)
BCM U1096
SDM U1016
RFA U1016
HVAC U1160

I also noticed the headlights did not want to go down last night unless I fired the car back up and turned them off (because I forgot to turn them off from my test cruise). With the key off, the headlights would turn off but remained in the UP position. After starting the car up, I was able to get them back down. Also, at some point idling the car, I noticed my tach needle was jumping up a few times without my foot being on the throttle. Car has a brand new Optima red top battery and a heavy duty alternator, though I have not tested either one.

Edit: also the ignition seems a bit flakey--I can remove the key from the ignition but still hear the "chime" and the DIC is still lit up. I have tried pushing the key in/out several times to see if maybe the plunger is sticking or bad somehow.
Edit 2: I keep thinking of more weird behavior to point out... when the car shuts the throttle or stalls, I also lose my datalog every time. If I'm scanning with HPT, the log will stop and I'll have to restart. It loses communication.

Where to start?

 

The car definitely makes some heat, it's a TTIX twin turbo setup so it has a turbo close to the starter etc.

 

And btw, car seemed to go back to coolant temp every time when restarting since that's what I keep it on .

 

Bueller?

 

Lots of good help in here... LOL. Could the battery still be an issue even though it's new and shows over 12V on the gauge? (always cranks up quick)

 

Hmm. That sounds like a bunch of seemingly unrelated electrical issues.

What data logger are you using? Can it be put on its own dedicated power supply (a separate battery)?

Wide-ranging electrical issues are often supply issues (battery, alternator, or the big red cables attached to 'em) or a ground issue (check all your ground wires.) Can you check for continuity on all your wires, with the car off, and then check for voltage drop with the car on?

 

I believe the "Rev Limiter"..." Fuel Cut Off" ....on the Z06 is 6500 RPM.

 

Using HP Tuners for datalogging. Have checked most of the ground locations already. Had battery tested tonight and it was good.

LOL, it didn't hit the limiter and the Rev limit is higher than stock now. Datalog shows throttle closing at 6000.

 

If you are loosing DATA LOG capability, you could be having a SERIAL DATA BUSS issue Engine is most likely going into reduced power. When it happens, are you seeing any messages in the DIC???

Have you tried to read the DTCs when the engine is in the problem mode ( prior to turning off the ignition) Just press reset until any and all messages in the DIC are gone and then enter the DTC reading routine. Post those DTCs.

If its not a serial data buss issue, it could be that the ignition switch is intermittent and loosing it ability to provide the PCM/ BCM proper HOT in RUN and START power. It would be JUST LIKE you switch off the ignition. Funny thing when that failure happens, "IT DOESNT SET ANY ODD DTCs because it thinks you shut down the ignition.

Just brain storming...

Bill

 

So,, what causes a loss of serial data??? The MOST COMMON thing is the LDCM and or RDCM power connector inside the rubber accordion tube between both doors. Pop out the rubber tube, fish out the two connectors and look at the SIX PIN POWER PLUG. Separate the connector. Examine the six FEMALE PINS. If they are spread apart, they could be causing the serial data buss corruption issue.

It could also be the seat power plug is damaged and doing the same thing. Check all three and see if there are any SPREAD APART female pins that are making poor connection with the male pins.

Bill

 

Bill, thanks for chiming in! Was hoping you'd see this. The car does not say reduced power in the DIC when this happens. I have been checking the codes through the DIC before shutting the engine off so that's what I listed above. My friend took the ignition switch apart and polished the contacts (I believe from looking at one of your threads) but no change. Could the ignition switch still be bad? I know the car chimes even after you pull the key as if it thinks the key is still in it.

Btw, had battery checked last night and it tested good.

 

Here are all the codes I've seen come up as I've been working through this, it's crazy:
TCS U1016, C1232, C1283, C1276
RADIO U1016, U1096
BCM U1016, U1096
SDM U1016, U1096, B0026, U1040
RFA U1016, U1096, U1255
RDCM U1064, U1096
LDCM U1096, U1064, B2282
IPC U1088, U1016, U1064, U1040, U1176
HVAC U1160, B0361
SCM U1300, U1255

 

Well,,,,,,,,,,,,,,,,,,,,,,,,,,, You sure do have a serious U series DTC issue and that tells me you are having some sort of serial data buss issue..

I don't know what opportunities that you have to repeat the same WOT situations that make the issue happen BUT,, I would like you to try this:

To the LEFT of the BCM are TWO slim connectors (STAR 1 & STAR 2 ) The STAR connector with FOUR wires controlles the serial data lines for the LDCM, RDCM and the SCM. Pop the top shorting buss of the connector and leave it off. Test the car with it OFF and see if you get any better results.

With the four wire STAR connector OPEN, you will not have any serial data to those modules but ALL the other modules SHOULD perform normal. Those three modules cause the most serial data issues in our C5s and this will isolate them.

Bill

 

SCM....U1300....MMMM ??...U1300 is a "short to ground" on the data line...can't really check the serial data line voltage with a multimeter (purple wire of the DLC) but you can remove the battery cables (you don't want the modules to wake up while ohming out the wires) and OHM out that purple wire (pin 2) to either pins 4-5 on the DLC...Key Off.... if the resistance is less than 350 OHMS yeah, you have a short !!

 

On a second note,, The C-1232 & C-1283 DTCs need addressing.

Pretty easy to get rid of!
C-1232 LF Wheel speed Circuit open or shorted. Theres a JUMPER HARNESS between the wheel hub and the EBTCM on both front wheels. Its about 2 foot long. There are TWO connectors between the wheel hub and the body harness connector that have FEMALE PINS in it, The female pins inside those connectors are WELL KNOWN to spread apart and male POOR CONNECTION with the male pins. Simply remove the jumper harness and inspect the femal pins in the jumper harness and inside the cars main harness where it connect to. If the pins are spread apart, use a pick or something to make the little tab inside the female pin to bend back out and make more firm contact with the male pin.

DTC 1283. Excessive time to Center Steering!! Kind of IMPORTANT and can cause the car to react very ABNORMAL.. It can cause the brakes to apply when you are going straight down the road. NOT A PLESNT EXPIERENCE

Simple repair. Have the car properly aligned and once its aligned, have the alignment tech CENTER THE STEERING WHEEL so that its perfectly straight when going straight down the road.

Let me know what you think.

Bill

 

FYI....vid on the issues you may be having !!...good luck !!

 

LOL! YES, our driver seat power connector gets abused a LOT.. People don't always reattach them properly and they get damaged when the seat moves. There is a serial data line in that connector and it can easily short to other pins.

Give that a close inspection and report results.

Good catch RWOBS777

 

We disconnected Star connector 2 to no avail. Symptoms continue.
When disconnecting connector 1, will the car still crank and run without data between pcm/bcm?

All ground connectors have been checked and look to be brand new. (This car has lived in the garage and was rarely driven)
The car has a somewhat rough idle/miss, and will shut off on its own randomly. It seems to be getting worse as time goes on?

 

 

Messed with the car a little bit today.

Star connector #1
Disconnected star connector #1 and jumpered the bcm and pcm together. The car started, spit and sputtered and shut off.
Re-connected star connector #1 and cranked car again with same basic outcome of the car running rough and shutting off a few seconds later.
Checked all the terminals in star connector for continuity to ground. None were grounded.

Bad connection in fuse box?
After a few starting attempts, the starter simply gave a "click" and refused to turn the engine over. Battery showed 11.8v at this point.
Cycled the key a few more times with the same no crank result and noticed the fuel pump was no longer priming in the run position.
Noticed in the run position the injectors? and a relay making a buzzing noise. Bumping the under hood fuse box made the sound change pitch and fuel pump started working? Car was then able to crank. Are we onto something here?
Battery was tested at the parts store and is good. It is brand new also.
Alternator was putting out around 14.2 volts when i checked it recently. (when the car would actually run)

Attempted logging with HP tuners
We do not have access to a tech II, but we do have HP tuners. We plugged into the car to see what looked abnormal.
Some values seem dead/missing and response is slow. However, laptop shows to be connected and "logging".
Depressing the accelerator shows no change on the screen. how could that be?


Thought- The car recently had the engine harness plug disconnected from the underside of the fuse box for some maintenance. It is firmly in place with the bolt tightened now, but i am wondering if there could be a loose connection in one or more of the terminals in there? it sure seemed that way when it responded to being bumped...... or was that a fluke?
Could a loose connection in the fuse box impair communication from a laptop to the pcm? Or the throttle position?