I have a problem with my 08 intermittently throwing two codes (service reminders). Sometimes it is service anti lock brakes and other times it has been service active handling. It doesn't do this every time it is driven. When I took it the dealer they found no codes. The only thing they found was a weak battery which was replaced. Next day I start the car and there is a service anti lock brakes message. I drove the car about 40 miles and parked it for several hours. When it was re-started there were no service messages. anybody got any ideas why the car would show these two service reminders and there is no record of a problem stored in the ECU??

 

There _should_ be codes stored in the EBCM that can be retrieved with a Tech 2 or the like.

It could be anything, but for intermittent ABS/TC/AH problems of this sort one easy thing you can try is the following: lift up the passenger footwell panel to access the BCM. Unplug the two big blue connectors. Drench them in spray-on electrical contact cleaner. Plug them back in.

 

It's possible for one of the wheel speed sensors not responding at times.
Could be just a dirty connection at the sensor.

 

some codes will go away after so many starts

as soon as you pop a code head on over to any auto parts store like Auto Zone, O Riley etc and have them read the code . Don't wait........
without a code you are just guessing at what could be wrong as there are several things that will pop up the same error messages on the DIC...

Dave

 

Some ABS codes will go away after the engine is turned off. Active Handling codes are primary examples of that scenario.

All 3 functions of the ABS are located in the EBCM not the ECU. Those are ABS, Stability Control (Active Handling) and Traction Control. If you are getting a message that indicates you have an ABS problem that means the problem is only related to the ABS and doesn't affect the other two functions.

The next time you have a message don't turn off the engine and see if you can get somebody with a code reader that can read OBD II and ABS codes to read the codes. Some auto parts stores will do that for you. Once you know the codes don't blindly replace parts because the code name is equivalent to a part name. Codes only tell you where to look for problems not what the problems are.

Voltage levels can definitely affect the EBCM so you need to make sure not just the battery is in good shape but that all connections from the battery to the EBCM are in good shape both on the voltage and the ground side. That means inspecting connectors and connector pins to make sure they are clean and making contact and checking ground wires where they connect to the chassis.

Don't act on somebody telling you it is a wheel speed sensor unless you know it is one. Even a code that tells you a wheel speed sensor is bad doesn't account for a bad connector between the sensor and the EBCM. The other thing is if you have a wheel speed sensor issue that always affects all three functions and you would get constant warnings about servicing ABS, AH and TC. From your description of the problem with only two of the three functions being affected I doubt you have a wheel speed sensor issue so I would start some place else like making sure the voltage/ground and all signal lines are clean and making contact.

The steering sensor, yaw sensor and lateral G sensors can affect AH without affecting ABS or TC. In fact that is how I got around the C6 TPMS issues when I didn't have TPMS in my track wheels. I pulled the connector on the steering sensor and that deactivated AH so it couldn't apply the brakes at speeds above 55 mph when there were no sensors. I still had ABS and TC but had to manually turn off TC by pushing the button on the console.

Bill

 

Some of these codes/eratic electrical alarms or gremlins might well be cause by connector pins fretting, and not always making full contact between the male/female connector.
The area to check is under the passenger floor board and the blue connectors at the electrical fuse panel.
If a passenger pushes hard on the floor board, the connectors can get shifted and this can cause the fretting and occasional alarms.
See the attached PDf for pics and further explanation.

Good luck

 

The way this is written, it can be misconstrued that C-code faults are isolated from P-code faults and cannot originate from anywhere but through the BCM. Although I agree any hard faults that are C-Code faults come through the BCM canbus path, there are several ECU generated P-Code faults that will also generate Service AH and TC messages and will have nothing to do with faults or intermittent faults in components on the BCM path.

Almost any P-code fault related to "drive by wire" that originates in the ECU with generate the service messages AH and TC. These faults are too numerous to list here but a very small sample:

P0220 Throttle Position (TP) Sensor 2 Circuit ECM
P0222 Throttle Position (TP) Sensor 2 Circuit Low Voltage ECM
P0223 Throttle Position (TP) Sensor 2 Circuit High Voltage ECM
P0502 Vehicle Speed Sensor (VSS) Circuit Low Voltage ECM
P0503 Vehicle Speed Sensor (VSS) Circuit Intermittent ECM
P1516 Throttle Actuator Control (TAC) Module Throttle Actuator Position Performance ECM
P2101 Control Module Throttle Actuator Position Performance ECM
P2119 Throttle Closed Position Performance ECM
P2120 Accelerator Pedal Position (APP) Sensor 1 Circuit ECM
P2122 Accelerator Pedal Position (APP) Sensor 1 Circuit Low Voltage ECM
P2123 Accelerator Pedal Position (APP) Sensor 1 Circuit High Voltage ECM
P2125 Accelerator Pedal Position (APP) Sensor 2 Circuit ECM
P2127 Accelerator Pedal Position (APP) Sensor 2 Circuit Low Voltage ECM
P2128 Accelerator Pedal Position (APP) Sensor 2 Circuit High Voltage ECM
P2135 Throttle Position (TP) Sensor 1-2 Correlation ECM
P2138 Accelerator Pedal Position (APP) Sensor 1-2 Correlation ECM
P2176 Minimum Throttle Position Not Learned ECM

When these faults and others originate in the powertrain, AH and TC are suspended and the warning messages notify the driver NOT to rely on these systems. As soon as the powertrain fault is fixed, AH and TC are restored. These two messages cause so many misunderstandings for the layperson as they are interpreted as separate and isolated failures when in conjunction with a CEL, but they are not. In fact, when the ECU suspends AH and TC which display as service messages, no codes are set which also confuses some even when they have access to a scan tool capable of reading B, C, P, U-Codes.

Conversely, when AH and TC (and some ABS) are activated, many of the actions to regain control occur from signals passing through the BCM and into the ECU, the primary action of which is the control of throttle position (can also be a combination of spark control or fuel cutoff) which are all ECU functions. Even the AH and TC thresholds are set and established as ECU functions and those data reside in the ECU.

 

Thanks BlindSpot for the comprehensive post. I have been out of town since 9/21 so have not been able to follow up. One thing I am fairly sure of is that the dealer Bachmann Chevrolet here in Louisville doesn't have anyone who knows how to troubleshoot this problem. I will first check the blue connectors under the passenger floorboard.

 

Take a look at this thread (https://www.corvetteforum.com/forums...ops-in-ky.html). Notice the name Hunt keeps coming up as an indie shop. Then, look at this and esp. the first para (http://www.huntandknight.com/). Good luck.

 

I had service active handling displayed and fixed it by securing the large connector under the adjustable steering column. I used tie wraps.

 

Finally solved: It turned out to be the right rear wheel sensor (no problems in connectors). It was so intermittent that displayed problems (service active handling, service anti-lock brakes, service traction control) were gone by the time I could get it to the dealer. Finally the service reminders stayed on all the time. The right rear wheel bearing was also failing so I had both rear wheel bearing assembly's replaced. Car is back to 100%. I did check the connectors under the passenger floorboard as suggested and cleaned the harness plugs as suggested but did not solve problem. Thanks to all who answered and made suggestions.

 

Thanks for taking the time and posting back that your issue is finally solved.
Maybe the bad bearing had something to due with the failure, as metal dusting from bearings is usually seen when they do go bad, playing havoc on the signal on the sensor. Something I will keep in mind in the future.

 

My 2008 is throwing the ABS, SC, and TC codes. My mechanic diagnosed it to be the right front wheel bearing/hub assembly. He said that his case log in the diagnostic system showed that the right assembly has shown more issues than the left. Additionally, GM has redesigned the part. Part number 88967287. The new GM part alone is over $500 and about 2 hours labor.

My codes were not intermittent and occurred without a passenger. I have extremely low mileage on the vette and it is not driven in conditions other than sunny and dry. So, if this continues after the part replacement, I will be following the procedures above.

Thanks.

 

I had a right front wheel bearing fail at 15000 miles. I think this a fairly common problem on this vintage Corvette. Thundar like you me 08 is only driven in dry conditions.

 

UPDATE: Well my mechanic did find a sensor issue with the Right front wheel bearing/hub assembly and replaced it. The codes still fired. He had active monitoring setup and watched all wheel signals as he was driving. The sensor signal was resolved, but he was still getting the ABS/TC/AH error. He also replace the battery, since this was original and it did not have significant amps left for a cold start.

He believes that it is beyond the connectors, grounds, etc., but with the control module. He switched out connectors from left to right on the new wheel bearing and still got the error on the right wheel. Does anyone have any insight to a company that does module repairs. I see many for sale on Ebay, but they appear to all be salvage. I assume that they would also need to be programmed by a dealership too unless it is my original module, correct?

Any direction would be appreciated.
Thanks.

 

Swapping harnesses left/right is a good diagnostic technique. Certainly sounds like the problem lies in the BCM. Has to be BCM since you're getting all three errors - TC/AH AND ABS.

This is a longshot, but look up DSX Tuning. He is a forum vendor. Talk through this and see if he might offer some module help.

 

I would think that the EBCM controls problems that the poster is having issues with

 

Which DTCs and symptom codes are currently set?

 

My mechanic said it was throwing a C0040 code. Not sure if that was the only one.

I currently have the Vette back with me, he wanted to do some homework and I didn't want it sitting out. I really don't want to go to a dealership if I don't have to. I have not had quality experiences with any of them. Even oil changes, but that is another post. LOL.

UPDATE: 10/30/17
My mechanic did some homework on the EBCM for my 2008 and he found that GM discontinued a replacement part. The shelves are clear on this one. So the only option is to find an aftermarket, used part, or repair original. Unless it is the original, it will need to be re-initialized to the vehicle (GM Dealership).

Going forward, he is confident we have an issue with this module. He was reading consistent signals from all wheels after installing the new RF wheel speed sensor, but the dash was still showing the ABS/TC/AH message. As I mentioned earlier, he even switched the wiring harnesses between RF and LF and still saw the RF issue. There might be a chance of some sort of interference on the RF speed signal, but there was no misfiring of the vehicle.

At this point, I am seeking someone that repairs the EBCM so we can pull it and send it out. Once we get it back we can determine next steps.

Any opinions, recommendation, or ideas welcome.

 

It would be instructive to actually look at the signal from the RF wheel speed sensor on an oscilloscope. Everything else is shooting in the dark.

It's possible the plug wires or coils are inducing some sort of interference on the speed signal. Make sure the wires are seated and that the engine isn't misfiring.