I was on my way to a Dyno Day this past Friday, and of course for my 1st vette event in a while my CEL comes on! After 3 stop-start cycles the light turned off on it's own. I checked them just now, and this is what I got:

P0102H Mass Air Flow (MAF) Sensor Circuit Low Frequency
C1221 LF Wheel Speed Sensor Input Signal is 0
C1222 RF Wheel Speed Sensor Input Signal is 0
C1248 ???

I couldn't find the last code listed in the C5Z Faq Sticky. I cleared the codes so I can't double check but I'm sure that's what it was. I've gotten the code for the MAF before, but not for the Wheel Speed Sensors. What would cause that?

 

If you ran it on the dyno, that is what set the wheel speed codes. Did the same thing to mine. C1248 set because because of the other two wheel sensor codes. Here's the GM Code 1248 diagnosis.





DTC C1248
Circuit Description
The dynamic rear proportioning (DRP) is a control system that replaces the hydraulic proportioning function of the mechanical proportioning valve in the base brake system. The DRP control system is part of the operating software in the EBCM. The DRP uses active control with the existing ABS in order to regulate the vehicle's rear brake pressure.

Conditions for Running the DTC
One or more faults have been detected by the EBCM in the ABS/TCS systems.

Conditions for Setting the DTC
One of the following conditions exits:

• DTC C1236 sets and ignition voltage is less than 8.5 volts.

• DTC C1254 or C1255 sets.

• DTCs C1265 and C1267 set.

• Two wheel speed sensor DTCs on the same axle set.

Action Taken When the DTC Sets
• The EBCM disables the DRP for the duration of the ignition cycle.

• The red Brake warning indicator turns ON.

Conditions for Clearing the DTC
• The condition for the DTC is no longer present and the DTC is cleared with a scan tool.

• The EBCM automatically clears the history DTC when a current DTC is not detected in 100 consecutive drive cycles.

Diagnostic Aids
• Use this DTC in order to differentiate which of the following conditions is present:

- The EBCM turned ON the red Brake warning indicator.

- The instrument cluster turned ON the red Brake warning indicator due to low brake fluid in the master cylinder reservoir.

- The instrument cluster turned ON the red Brake warning indicator due to the application of the park brake.

• Diagnose any other ABS DTCs that set along with this DTC.

Test Description
The number below refers to the step number on the diagnostic table.

Verifies whether other ABS/TCS/VSES DTCs are set.

Step
Action
Yes
No

Schematic Reference: Antilock Brake System Schematics

1
Did you perform the ABS Diagnostic System Check?
Go to Step 2
Go to Diagnostic System Check - ABS

2
Install a scan tool.
Turn ON the ignition, with the engine OFF.
Select the display DTCs function on the scan tool for the EBCM.
Does the scan tool display any ABS/TCS/VSES DTCs?
Go to Diagnostic Trouble Code (DTC) List
Go to Step 3

3
Use the scan tool in order to clear the DTCs.
Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.
Does the DTC reset?
Go to Step 2
Go to Testing for Intermittent Conditions and Poor Connections in Wiring System

 

RAMMAN thanks! That's what I was looking for, you da man!

But the engine light come on before the car was on the dyno, on my way up to the shop in traffic during commute hours The light had cleared by itself just as it was going on the rollers.

 

Thanks, you said you had had the MAF code in the past. That is what turned on the check engine light.
The other codes would have given you a traction control warning on your DTC. As I'M sure it did on the dyno.
Clear everything and the next time you get a warning pull over and use the DTC to pull the codes . In diagnosis of computer control problems often times one code sets another. You always should try to determine the first code to get to the root of the problem.
If you have an after market air intake set up they have been known to cause codes to be set on the 02'-04' ZO6's. The non screened MAF is very picky, I ended up retuning mine to stop the problem.

 

I've got a Halltech Stinger, and I know what you mean about the non screened MAF. After I got a tune the MAF code has only come on once in 2 years. But I guess the codes for the Wheel Speed Sensors tripped the MAF code again? Right?

And ya I think the TCS came on a couple times extra on the way up to the shop, I was cruising with a 07 Z06 the whole way.

 

Hi
I installed Dynamaxx headers and Vara ram on my A4 01 had it dynoed

I have gone thru 3 sets of sensors --Check engine light comes on with code BO RFA U1064 I can clear - get H and C - check engiine light keeps coming on - dealer replaced senors 3 times - warranty company is getting upset
Any help
Len