BlackZ06

If you got the SERVICE ABS/TC/AH messages, you have HISTORY codes set in the EBCM. In fact the codes are set to H status at the end of each ignition cycle. They will remain in the EBCM for 100 ignition cycles of no re-occurance.

I suspect you either didn't pull codes correctly, as every Corvette has at least a few Uxxxx codes, and you definately have one or more CxxxxH codes if you got the SERVICE messages, or you didn't realize that H codes are left in the computer as a diagnostic aid for intermittent problems.

BCAM

I haven't pulled the codes at all. I didn't realize they would remain in the EBCM. That's an interesting and quite useful bit of engineering there. I will pull them and post them.

Thanks

BlackZ06

So would you like to take back the "I appreciate the advice but lose the "i'm the expert big brother here."" statement ???


The fact is the C5 Corvette is a VERY sophisticated collection of computer hardware/software .... GM has done a HORRIBLE job of marketing how sophisticated the systems are in their cars. Look at the RPO F55 suspension option ... so good that Ferrari has licensed it and uses it in the 599 GTB Fiorano, and Audi has licensed it and uses it for the new R8.

The computers in a C5 manage almost every function in the car ... and if they don't manage it, they monitor it ... and post a Diagnostic Trouble Code (DTC) when they see a problem.

The format of the codes is AxxxxZ where A=the type of code (Powertrain = P, Chassis = C, etc.) followed by 4 digits, and at the end is either a C or H (sometimes both for certain codes) indicating if the problem is Current or History.

These cars are VERY complex .... there are many computers in them, and almost everything that occurs requires interactions between at least two computers .... turn on your A/C and you are "requesting" A/C ... it is ultimately the PCM that decides whether or not it is willing to turn on the A/C compressor, and it is programmed to "throttle up" the engine as the A/C compressor comes on-line so that you don't feel that "hesitation" as the compressor clutch engages.

If you have a "problem" with the car, the best thing to do is to dump the DTC data .... it goes a long way toward helping pinpoint the problem.

Tom Steele

Yeah, I know. That's why I came here - to see what service is needed so I can do it. Preferably myself. Looking at the other thread on this, I'm going to go through all the grounds with a fine tooth comb this weekend.

As I said, I don't use AH or TC. I find them to be next to useless. But I do like ABS. I don't want to flat spot a set of $1,200 tires in a panic stop.

The search is what brought me to this thread. I discovered some of the others as I continued down my search results. This one was first.

Thanks, saved me looking that up. I haven't checked my codes in ages.

As you can see from my sig, I'm basing my opinions on 8 1/2 years of C5 Corvette ownership, most of them with the Z06. I'm not at all impressed with the AH or TC on these cars. It is blunt and heavy handed in most cases. I'll be impressed when they come up with one that can improve my driving without shutting the car down most of the time. (And they will, they just aren't there yet.)


To each his own.


Again, not in my experience. I'm not impressed with the C5 implementation of AH, or TC. Heck, I think they could improve the ABS but at least it does what it is supposed to do.

I generally save my own. AH and TC are relatively new things. I've been driving for long enough that I learned how to drive without a nannie shutting down the throttle when I choose to put the car into power oversteer and while no one is perfect and I can't claim I've never made a mistake - I haven't wrecked yet. And I find limits from time to time...

djstylze

Guys.. absfixer.com

150 shipped.

BlackZ06

Since neither of these posters has listed his DTC data ..... what makes you think the problem is in the EBCM ?????

If it is a wiring problem to a wheel speed sensor, or the Steering Wheel Position Sensor is failing, then they've just spent money for nothing .... let's do a little diagnosing before jumping to a "fix" ....

djstylze

Fair enough, just thought I'd throw that idea into the pot. I think the OP should always take the free/easiest fixes first before repairing a part.

For me, I went through 5 different ideas before I fixed it with the absfixer guy. I just scanned the replies and saw no mention of it.

RICHARD D. HUDSON SR

Just Had Same Problem With My Z . It Was The Wheel Postioner Sensor. Which Is Located At The End Of The Steering Column Under The Dash ,driver Side. Part From Gm Cost $20.took Z To Gm For Install 1.5 Hr. Got The Z Back . No More Codes Or Problems. Do A Search In Wheel Postioner Sensor For More Info. Good Luck!!

Blue Blood

Since we're all family here and I'm having the same problem, here's my codes, C1214 and C1287. Any suggestions?

fxdl

i think mine had the c1214 code. had to replace the ebcm. all is well. the part is easy to get to. right on the abs pump. kind of expensive though.

BlackZ06

C1214 - The dreaded "BPMV control curcuit" relay .....

C1287 - The SWPS (Steering Wheel Position Sensor) input is invalid

Given that it seems unlikely these would both fail at the same time, here's what I would recommend.

Step 1) Check the EBCM grounds and be certain they are clean. The EBCM is grounded at two points, G103, and G108. The EBCM provides the "ground" for the SWPS ... there is no seperate ground for it.

G108 is located on the right frame rail, next to G104, almost directly below the NEG battery cable.

G103 is located on the left frame rail, just behind G101, and about opposite the BPMV.

Step 2) After cleaning the grounds THOUROUGHLY, and checking the EBCM wiring connectors for corrosion, DELETE the codes from the EBCM using the DIC. Clear ALL codes from the car.

Step 3) Go out for a drive - 15 minutes or so, no need to do anything "aggressive", if the relay that sets C1214 is actually failed, the code will come back within seconds of your engine starting (and your foot is off the brake pedal).

Step 4) Check for codes at the end of the drive. Post here if there are any. If none ... very cool. If the C1214 is back, take a look at either replacing the EBCM with another from GM (which will eventually fail too) or sending in your EBCM to http://www.absfixer.com and getting the problem fixed once and for all.

BCAM

Sure, I'll rescind my statement. Perhaps first impressions got us off on the wrong foot. Apologies.

I apologize that I haven't posted the DTCs yet. Just hasn't quite made it to the front of the priority queue yet.

-B

Blue Blood

two weeks ago I had the dreaded column lock rear it's ugly head. Had to tow the car to the local dealer where they replaced a couple relays and the column lock actuator. I was getting the ABS/AH codes at the same time but they couldn't get them to come back after the column lock issue was repaired. Is this stuff all related by any chance?

I located and cleaned the grounds on the frame at the front of the car by the radiator, are these the ones you are referring to?

Thanks for the assist, Clint

BlackZ06

No problem ... sometimes we all have our "bad" days ....

Post the codes when you can and we'll look at them ....

BlackZ06

The ones on the front frame, drivers side, is the G103 location (by the radiator). G108 is on the other side (passenger) and further back, almost directly below the battery NEG cable.

The Corvette is different from most cars in that effectively it is a "plastic" body on a metal chassis. The reason this is important is that on your "average" car any electrical component can be grounded directly to the bodywork (metal) it is attached to. On the Corvette the ground has to actually be a wire that leads back to a location on the chassis. If these ground locations become corroded, or a wire comes off, then the component being grounded no longer works correctly, or works intermittently. With all the computers in a modern car, a bad or intermittent ground in a few components can cause all kinds of confusing and seemingly unrelated problems. Keeping the ground points clean on a Corvette helps a lot.

Also, voltage is important. The computers expect to see a consistent voltage level from the sensors and other devices they control. A weak battery can also cause seemingly unrelated and unexplained problems. Always check the NEG and POS battery cables when you are doing an oil change and be sure there are no signs of corrosion starting, or cables coming lose.

It seems unlikely the EBCM and the column lock issues are related, but certainly if you and/or the dealer cleaned ground points to address the column lock, that may have also cleared the EBCM issues. There are only a handful of groundpoints in the car, many are shared by numerous parts of the system.

It sounds like your EBCM is working OK now, DELETE those codes so you have a "clean" record, and keep on

Have fun out there ....

BCAM

Problem reared it's ugly head again this mornin...came scrolling across the DIC

**************************************** *********
Current Codes:

Module: 28 TCS Traction Control system ABS
Code: C1214 Sol Valve relay Contact or coil CKT Open

Historical Codes (had an 'H' next to them on the DIC):

Module: 40 BCM Body Control Module
Code: U1160 Loss of Communications with LDCM

Module: A0 LDCM Left Door Control module
Code: B2252 Key Cylinder Switch Fault DCM-LEFT

Module: A0 LDCM Left Door Control module
Code: B2284 Battery #2 Fault DCM-LEFT

Module: AC SCM Seat Control module
Code: U1064 Loss Of Communication with DCM (No SOH Message
Received -RFA

Module: A1 RDCM Right Door Control Module
Code: B2285 Battery #2 Fault DCM-RIGHT

**************************************** *********

I seem to have traction control problems in both my seat and in the rear wheels...

What say you?

BCAM

Looks like the strikes again...

Where to go from here....

BlackZ06

The Door Control and Seat Control Module DTC look like an electrical issue. Possibly at one point in time you had a voltage drop while starting the car (weak battery) and the seat was adjusting itself at the same time. I'd delete them, but watch for a re-occurance. Sometimes these can also be kicked off by the wiring in the "accordion" protection in the door hinge area. Occasionally the wiring inside thee accordion can chafe and short or ground .... if you keep seeing these type of DTC I'd look in the hinge area ....

I'd try cleaning the grounds at G103 and G108, then clearing the code and seeing if it comes back again. If it is intermittent, there is a chance that the grounding is the issue, as usually when the relay fails, it fails for good. Another thing you can try (after clearing the code) is taking the car on a quiet road and "exercising" the BPMV and the relay by making two or three stops that activate the ABS.

If the code won't clear, the best solution, in my opinion, is to ship your EBCM to

http://www.absfixer.com

The site includes instructions on removing the EBCM (the car is driveable with the unit removed) and shipping it.

BCAM

Thanks for the information. At what level is the AH/TC and ABS functioning now? Not at all? Also, what's the skinny on the functionality of the relay? (or a link will work )

BlackZ06

With a C1214 set, the EBCM is almost completely non-functional. The EBCM is unable to control the BPMV, which means that all of the EBCM functions that require it to control brake line pressure are disabled. This means you have no ...

ABS - Anti-lock Brake System
TC - Traction Control
AH - Active Handling
DRP - Dynamic Rear Proportioning
RSC - Rear Stability Control (2001 and later)

The EBCM continues to monitor/control your MAGNASTEER system, as it uses a different solenoid to control that system.

Basically you are driving a car from the 1960 era .... you have a brake system that works, but your foot is completely in control. There are no "nanny" aids such as ABS to come to your assistance in an emergency. Another way to look at it .... when/if you remove the EBCM and send it to absfixer ..... the car will drive the same (almost - steering effort may feel different) with the EBCM removed as it does today with a "disabled" EBCM. ALL of the above functions are COMPLETELY disabled.

The EBCM is basically a computer, it has no "mechanical" capabilities. The BPMV is a mechanical device that is able to either increase pressure in a brake line, or decrease pressure in a brake line, but it has no "brain" within itself that decides when to change the pressure in a brake line. The EBCM is the "brain" that controls the "dumb" BPMV. The C1214 simply indicates that the EBCM no longer has the ability to control the BPMV. Once the EBCM realizes it cannot control the BPMV, it sets the C1214 and "disables" (shuts off) all of the functions it controls through the BPMV.