Is there any way to test a wheel speed sensor on a C5? Over the off-season I replaced both fron hubs on my '02 Z06. The hubs of course include the wheel speed sensors. Now I throw the following codes:

• C1225 RF Excessive Wheel Speed Variation
• C1232 LF Wheel Speed Circuit Open or Shorted

When the codes throw I lose ABS/Traction Control/Active Handling. Unplugging the front-left wheel speed sensor, then plugging it back in seems to fix the problem for a short period of time. But even that's working less and less. Before I pull this hub back out and deal w/ warranty etc. is there any way I can test the sensor?

Perhaps it's just a bad connection? I looked and the 'pins' in the connectors all seemed fine but who knows.

-TJ

 

My neighbor, an ex GM tech, told me that brake dust sometimes coats the sensor making it give a reading out of range. He suggested I clean mine with Brake Cleaner.

I do not know if this is true, but thought I'd pass it on.

 

Hmmm, the thing is this is a brand new hub that started doing this before I ever even raced, or really drove much with the new hub in here.

-TJ

 

Can't do that on a C5. The sensor is sealed inside the bearing. On older C4s and other GM vehicles they can be cleaned.

Here is what is happening when you get the codes:

C1225 through C1228
The EBCM detects a rapid variation in the wheel speed. The wheel speed changes by 16 km/h (10 mph) or more in 0.01 second. The change must occur 3 times with no more than 0.2 seconds between occurrences.

C1225 through C1228
A possible cause of this DTC is electrical noise on the wheel speed sensor harness wiring. Electrical noise could result from the wheel speed sensor wires being routed to close to high energy ignition system components, such as spark plug wires.

C1232 through C1235
One of the following conditions exists for 0.02 seconds:

A short to voltage - the wheel speed sensor signal circuit and wheel speed sensor return circuit voltages are both greater than 4.25 volts.
A short to ground - the wheel speed sensor signal circuit and wheel speed sensor return circuit voltages are both less than 0.75 volts.
An open - the wheel speed sensor signal circuit voltage is greater than 4.25 volts and wheel speed sensor return circuit voltage is less than 0.75 volts.

C1232 through C1235
If the customer comments that the ABS indicator is ON only during moist environmental conditions (rain, snow, vehicle wash, etc.), inspect the wheel speed sensor wiring for signs of water intrusion. If the DTC is not current, clear all DTCs and simulate the effects of water intrusion by using the following procedure:

Spray the suspected area with a 5 percent saltwater solution. To create a 5 percent saltwater solution, add 2 teaspoons (9.9 ml) of salt to 354 ml (12 oz) of water.
Test drive the vehicle over various road surfaces (bumps, turns, etc.) above 40 km/h (25 mph) for at least 30 seconds.
If the DTC returns, replace the suspected wheel speed sensor or repair the wheel speed sensor wiring.
Rinse the area thoroughly when completed.

For the following tests you should use a good digital voltmeter. Preferably one with a 10 Meg Ohm input input impedance.

Disconnect the wheel speed sensor connector.
Measure the resistance across the wheel speed sensor.
Does the resistance measure within the specified range?
850-1350 ohms
Go to Step 4
Go to Step 8

4
Spin the wheel.
Measure the AC voltage across the wheel speed sensor.
Does the AC voltage measure greater than the specified value?
100 mV
Go to Step 5
Go to Step 8

You could also have an EBCM problem. Be sure to check all of the EBCM grounds, connectors (for corrosion), and wiring harnesses.

Bill

 

I think there is a second connector up by the frame - in addition to the one down by the wheel. Make sure it is clean and connected. The connector by the frame actually became loose on my 2000.

 

Check the female connectors at both ends of the front harnesses.
The connector on the left is new.

 

Thanks for all the advice! It looks like I need to just replace the harness from the chassis out to the wheel-speed sensor. The pins in the male connector out at the sensor had backed out, on in particular. I seated them back in and used some zip-ties to secure the wires to the body of the connector so they (hopefully) can't back out again. I plugged the harness back in on the sensor side then tested the sensor/harness as described above and the sensor tested out just fine. Everything is working great now! I think I'll replace the harness, or at least buy it and keep it in the trunk anyway.

-TJ