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I have a 2001 convertible and I am chasing a frustrating issue. I had my EBCM serviced by ABSFixer last month, when he sent it back, he noted the there was a C1228H code and indicated the right rear speed sensor may need replacing. Installed the module and have been getting the C1225H and C1228H regularly. I replace both rear hubs this week and cleared the codes. I still get the service traction control when accelerating harder than normal.
Yesterday, I took the car to a friend who has the GM scan tool. We hooked it up and drove the car around at various speeds watching the four wheels, they were all the same or within 1 mph of each other, then he saw the RR blip up 10mph and drop back down. We saw this happen a few times under normal driving. I jacked up the car this morning, took the RR sensor clip off and inspected the wires. all looks to be okay, I cleaned the contacts and added some dielectric grease.
Has anyone experienced this? Is there something upstream I can check? the leads run up into the wire loom and there were no obvious issues.
Last edited by R1-Addict; Jun 5, 2021 at 06:16 PM.
Reason: Update model year
First off please include in your profile the year of the car, mods, tune, and any other important info...if you know how to use a DVOM I would unclip the RR hub connector and check the BROWN signal wire (pic is from my ‘01 FSM) and with the key on you should see a 5 volt bias...many circuits in the car use a bias voltage and the PCM uses it to determine if there is an electrical fault on that particular circuit...the wheel speed sensors generate an AC voltage when spun but this 5 volt bias rides on top of it...the PCM knows that if the 5 volts drop to a certain level it knows there is an electrical malfunction in the wiring and a DTC will set...both wires from the speed sensors go to the EBCM so you can probe the brown wire with the key on and do a “wiggle test” to see if that 5 volt bias drops out or decreases...you should check that the terminals aren’t spread apart on both ends of the short harness...the other wire is a reference ground so you can disconnect the EBCM connector and use the ohm meter function and probe both ends of the circuits and do the wiggle test to see if the resistance goes from continuity to an open circuit !!...dielectric grease is an insulator so you should be careful where you use it !!
It could be the wires themselves. Cleaning and finally replacing the terminal ends only goes so far then you have to spring for a new wire. But it comes with new connections!
To check if it's the wire, swap the two rear wires side to side and see if the code moves with the swap.
If it doesn't move you lost about 10 minutes time and no money.
Thank for the replies, there some good information here. Does anyone know if the rear wires run from the plug all the way up to the EBCM, or is there a brake in there someplace like a pig tail?
Changing the connectors is a no brainier, that should have occurred to me as I trouble shoot networks all the time...
Thank for the replies, there some good information here. Does anyone know if the rear wires run from the plug all the way up to the EBCM, or is there a brake in there someplace like a pig tail?
Changing the connectors is a no brainier, that should have occurred to me as I trouble shoot networks all the time...
i thought you installed new wheel bearings and speed sensors? Chances of a bad connector out of the box is slim.
Thank for the replies, there some good information here. Does anyone know if the rear wires run from the plug all the way up to the EBCM, or is there a brake in there someplace like a pig tail?
Changing the connectors is a no brainier, that should have occurred to me as I trouble shoot networks all the time...
If you look at the wiring you can see A-C and B-D represent the short harness...beyond that no other connections...if there were it would be shown. A little FYI... the infinity looking symbol means these wires are a “twisted pair”...twisted together to present EMI in the wiring !!
Thank for the replies, there some good information here. Does anyone know if the rear wires run from the plug all the way up to the EBCM, or is there a brake in there someplace like a pig tail?...
Searched your post and don't see what model year car you have as there are significant differences in the wiring for this system from the model years....please update your profile with your model year car so that the members of the CF can provide you specific tech data for your model year car.
To get you in the ball park in resolving your issue; there is a connector ID C148 that your will have to take a look at. This connector is located in the battery compartment and to gain access to this C148 connector, remove the battery and battery tray, see below. Post up any findings after inspecting the C148 connector (male/female pins).
Cheers,
Goose
Searched your post and don't see what model year car you have as there are significant differences in the wiring for this system from the model years....please update your profile with your model year car so that the members of the CF can provide you specific tech data for your model year car.
To get you in the ball park in resolving your issue; there is a connector ID C148 that your will have to take a look at. This connector is located in the battery compartment and to gain access to this C148 connector, remove the battery and battery tray, see below. Post up any findings after inspecting the C148 connector (male/female pins).
Cheers,
Goose
THANKS !!…I didn’t even see C148 on my own wiring schematic !!
Searched your post and don't see what model year car you have as there are significant differences in the wiring for this system from the model years....please update your profile with your model year car so that the members of the CF can provide you specific tech data for your model year car.
To get you in the ball park in resolving your issue; there is a connector ID C148 that your will have to take a look at. This connector is located in the battery compartment and to gain access to this C148 connector, remove the battery and battery tray, see below. Post up any findings after inspecting the C148 connector (male/female pins).
Cheers,
Goose
Seeing how we just had all of those connections apart two months ago swapping my engine, that would make sense to check!
Excessive wheel speed variation DIC
