I have a strange problem with my 2002 Z06.

The car sets code C1226 Front wheel speed variance at speeds over 105 MPH. I discovered this while at the drag strip. I am going to a road race day in 2 weeks and want to solve the problem before then as when the code sets I loose my ABS and active handling.

Here is what I have done so far:

As there is some confusion it seems on the DTC lists on if C1226 is for the left or right front tire I checked both.

Left wheel sensor resistance 1126 ohms, right wheel 1223 ohms.
I can achieve over 100mV AC easily by spinning the tire as fast as I can.

I have cleaned the sensor connectors on left and right front with contact cleaner.
I have cleaned the short wire loom connector that connects the sensors and confirmed the prongs seat tightly.
I have disconnected the short wire looms and cleaned the connectors and checked the prongs. I took my voltage and resistance checks from here as well and they agree with what was measured directly at the sensors, so I thing the short looms are ok.

There is some talk of high frequency noise from the ignition wires but I do not think this is happening as at the drag strip I went to red line in 1st, 2nd and 3rd and did not set the codes. I believe this is speed dependent unless someone thinks it is the time you spend at high RPM in fourth that does it. Anyone have the routing of the cables so I can verify they are not near ignition sources?

I do not have a scan tool to monitor while driving. I risk my license every time I check to see if it is still happening . I did all the cleaning and checking this morning, cleared all history codes, ran to 110 mph and it came in. I cleared the codes and tried again and like clockwork it came in at just over 100. Tried 3rd time with same results.

Do I bite the bullet and replace the bearing/sensor? Which side? I need to confirm if C1226 is left or right. Can I swap the bearings from side to side and see if the problem switches side?

Help!!! My road day at mosport is 2 weeks away. If the instructor sees my IPC light up like a Xmas tree when I hit 100MPH I am afraid they will turf me from the session.

 

I'm pretty sure the hub and bearing can be swapped side to side.

 

here's some info I Googled:

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If I remember correctly, a tire out of balance, a loose connector, water in the connector, pinched wire, or a bad wheel bearing can cause this code to display.

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Check your tires. Excessive tire cupping on the tires can set this code.

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code C1226. Found Right Hub/Harness open circut (Hub & Bearing Defective) They replaced the hub & bearing assembly and repaired the wire harness sensor connector. (There was water in the assembly.) This has corrected my problem. However it was not cheap to fix.

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C1226 LF Excessive Wheel Speed Variation

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C1226 RF Excessive Wheel Speed Variation

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C1226 LF Excessive Wheel Speed Variation

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C1226 LF Excessive Wheel Speed Variation

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The code for the front right wheel was c1226

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Are the back tires taller than the front? I've heard running the same height tires causes codes

 

Are you using stainless steel brake lines? The brake lines actually provide the ground side of the circuit for the wheel speed sensors and some brnds (such as Russell) have been know to have problems. Try running a seperate ground wire from the hub to the chassis (just tape it on the brake lines for now) and see if that possibly clears the problem.

 

C1226 is for the left front. Do you have SS brake lines?

 

I had to ground my calipers (to the chassis) to solve a similar occurence on my s.s. line equipped '99.

 

Actually on the newer vettes 01-up I believe the C1226 is the RF wheel sensor circuit. Mine is doing the same thing. I replaced my short harness and my hub bearing and put dielectric grease in the connectors. I haven't gotten it up to that speed in while but need to soon just to see if it is fixed.

Do you use the active handling at the road racing events? Just curious. I went to a SCCA driving school and was told to start without it on. I like to have it on just in case, it has saved me more times than I can remember when I was goofing off.

 

Ive had the exact issue! The first dealer recommendation was the wheel bearing/sensor. That was WRONG! The next was the EBTCM. That fixed the issue, Then later on down the road, i had another issue. A right front wheel speed variation DTC.

I found it to be a bad connection. I used a male pin to check the female pin and found the passengers harness plug to be bad:



Without using a male pin to check the female pin, I would be still be figuriging out the problem. Everyone said it was a BAD wheel bearing and sensor. Now I have a spare good one!



BC

 

Bill put me on the right track. You have to check the females at both ends of the harness. In the picture below the connector on the left is new. C1226 is the right front.

 

Thanks for all the responses.

Some answers:

I do not have SS brake lines.
The tires are new <3k miles no cupping, standard sizes. I believe they are in balance because I get no vibration when driving.

I had seen the pictures of the connectors in other posts. Mine look like the new ones but I used a jewelers screw driver to ensure the pins were centered anyway. I also checked the femal connectors that go from the main loom to the short looms and they seemed OK.

I am night shift until Thursday. On Thursday I am going to swap the short connectors from side to side and see if the problem moves.

 

C1226 refers to the RF wheel speed sensor in all C5s. The problem may still be related to an ignition noise issue. Have you changed your plugs and wires recently? The wheel speed sensor develops an AC signal that increases in frequency with speed. Ignition noise coupled into the wiring harness may not bother the EBCM at lower speeds and frequencies but it may bother it at higher speeds especially if the frequncy of the ignition noise pulse is close to the sensor frequency. At 105 mph the noise pulses are probably occurring at about a third to a half of the frequency of the sensor signal and since they are pulses there are a lot of harmonics with them so there will be plenty of noise close to the sensor frequency.

Bill

 

Bill,

can I shield the cable? I read a post once on using aluminum foil to wrap the wire loom to shield from RF noise. I have only had the car for two months. I believe the wires are original as the car has only 20k miles on it.

 

For what it is worth, my fix for eliminating the code was replacing the harness (part # 10332527).

 

Does any one have the routing of the wires from the brake module to the wheel sensors? I would like to pull the connector off the brake module and measure the wheel resistance and millivolts right at the module connector. Pin numbers for this connectors to measure please.

 

I stand corrected C1226 is the right front. I checked my factory manual and it shows it as the RF. If you have a fax I can send you a copy of the pin arrangement.

 

Yes you can BUT,,,you will need to find a way to ground the foil to the frame. If you think the wires are bad, I would just replace them with a set of GM preforamnce Red Wires. They are inexpensie, high quality and durable.

BC

 

Here's the pin location on the EBCM connector!!
Connector Part Information

• C1 - 15318099
• 7-Way F Metri-Pack 480 Series (BLK • C2 - 1535670 • 29 Way F Micro-Pack 100 Series (GRY)

Pin Wire Color Circuit No. Function

A RED 1642 Battery Positive Voltage

B BRN 641 Ignition 3 voltage

C GRY 1787 Variable Effort Steering Actuator High Effort Control

D WHT 345 Variable Effort Steering Actuator Low Effort Control

E--Not Used

F BLK/WHT 1251Ground

G BLK 1250 Ground

1 Not Used

2 TAN/BLK 464 Delivered Torque Signal

3 LT GRN 176 Steering Wheel Position Signal A

4 Not Used

5 LT GRN/BLk 1338 Lateral Accelerometer Input (JL4)

6 LT BLU 20 Stop lamp Supply Voltage

7 Not Used

8 RED 885 Left Rear Wheel Speed Sensor Low Reference

9 BRN 882 Right Rear Wheel Speed Sensor Signal

10 DK GRN 872 Right Front Wheel Speed Sensor Signal

11 LT BLU 830 Left Front Wheel Speed Sensor Signa

12 ORN/BLK 463 Requested Torque Signal

13 ORN/BLK 556 Low Reference

14-16 Not Used

17 BLK 2626 Brake Pressure Sensor Signal (JL4)

18 LT BLU 1764 Steering Wheel Position Signal B

19 DK BLU 716 Yaw Rate Sensor Signal (JL4)

20 Not Used

21 LT BLU 1122 ABS/TCS Class 2 Serial Data

22 BLK 884 Left Rear Wheel Speed Sensor Signal

23 WHT 883 Right Rear Wheel Speed Sensor Low Reference

24 TAN 833 Right Front Wheel Speed Sensor Low Reference

25 YEL 873 Left Front Wheel Speed Sensor Low Reference

26 Not Used

27 GRY 1056 Steering Wheel Position Sensor 5V Reference Voltage

28 LT BLU 2627 Steering Position Sensor Signal

29 Not Used

 

There are two grounds for the EBCM module one of them is circuit 1250 which goes to G103 and the other is circuit 1251 which goes to G108. G103 is near G101 on the left side of the engine. 1251 goes through the forward lamp harness, to a ground point (G108) below the battery tray on the frame rail. 1250 provides a ground through the EBCM for the pump motor in the BPMV while 1251 provides a ground for the module. You should check that ground out also as it could cause a sensitivity to RF noise if it isn't in good shape. The wires from the sensors are twisted pair which should be somewhat insensitive to coupled noise but it might be a good idea to check and see if the previous owner/s did something to screw up the wiring for the right front sensor. The right front sensor signals 872 and 833 go through an in line connector C108 (RF wheel speed sensor to Transmission harness, mounted to the RH side of the front suspension crossmember) to C148 (Transmission harness to forward lamp harness, RH side rear of engine compartment, below the battery) then through the forward lamp harness to the EBCM.

Bill

 

Thanks for all the replies. I am going to get back at it on Thursday and I will let you know what I find