I recently diagnosed a CEL P0500 Vehicle Speed Sensor issue, and the root cause wasn't the typical damaged ABS wheel sensor. I learned a lot in the process, and I wanted to share it for the next DIY'er that might run into this.
Vehicle: 2006 Tribeca with 247,000 miles. The motor, tranny, and accessories are nearly identical to any of the H6 Outbacks and Legacys.
Symptom: CEL, cruise, along with ABS/brake dash lights. The dash also says "Err SS" which means Error Speed Sensor. The car runs in a failsafe mode where the radiator fans are always on. Vehicle is not in drivable state due to other issues so there was no information on overall drivability.
Check Engine code: P0500 Vehicle Speed Sensor
A few important things I learned:
So anyways, using FreeSSM with the vehicle's motor running I was able to pull C0023. I found a list of ABS/VDC C**** trouble codes somewhere on the net. I attached it here for reference:
This code pointed to the front left (drivers side) ABS wheel speed sensor. Great! That seemed like a simple fix. I decided to take a look at the speed sensor and the condition of the wiring. As I pulled the sensor out of the hub, I noticed it was all chewed up and missing chunks. The damage on the sensor was caused by the magnetic tone encoder ring on the back of the hub assembly.
Well that seemed like an obvious root cause. I ordered a new hub assembly and speed sensor, and I installed them. WRONG. It didn't fix it! I made a rookie mistake on not properly diagnosing the issue and throwing parts at it!
At this point, I found the FSM section on diagnosing Code 0023. It had me test the voltage going to the speed sensor (+12V one pin, GND on the other pin). I ohm'ed out the wiring through the various connectors on their way to the ABS/VDC module. All seemed good.
I guess the last remaining step was to replace the ABS/VDC module in the engine bay. I knew it had to be this module as the main ECU was talking properly to the ABS/VDC unit (via canbus) and no other errors were present. So I went to the local pick-n-pull and grabbed the ABS/VDC module for $45. Before bothering to remove all the hard brake lines into the old module, I simply plugged the cable harness into the new junkyard unit. Well, the error code immediately went away! I cleared out the codes and they never came back.
So there you have it. One cause of wheel speed sensor issues can be a faulty ABS/VDC computer modules. It's easy to do a proper diagnosis without any fancy or expensive tools.
Vehicle: 2006 Tribeca with 247,000 miles. The motor, tranny, and accessories are nearly identical to any of the H6 Outbacks and Legacys.
Symptom: CEL, cruise, along with ABS/brake dash lights. The dash also says "Err SS" which means Error Speed Sensor. The car runs in a failsafe mode where the radiator fans are always on. Vehicle is not in drivable state due to other issues so there was no information on overall drivability.
Check Engine code: P0500 Vehicle Speed Sensor
A few important things I learned:
- You can read check engine light codes on the Tribeca using the 06-09 Legacy/Outback method described here: http://www.subaruoutback.org/forums.../109-gen-3-2005-2009/19053-05-06-09-how-read-diagnostic-trouble-codes-dtcs.html
- On Subaru's, the P0500 code does not refer to the Vehicle Speed Sensors located in the transmission. The P0500 code actually refers to part of the ABS/VDC system, and you need to retrieve secondary cruise control codes to get more info.
- However, you cannot read C**** codes using the method from the previous bullet as the engine needs to be running for the ABS/VDC module to be responsive. When you use the method above and switch to the C**** codes, you will simply see the C---- blinking indefinitely. Not helpful!
- The simplest way to read the C**** codes (cruise control codes) is to use FreeSSM and a Vag-com ODB2 cable.
- You can get a cloned vag-com cable on Ebay for $8 shipped. Look for "VAG-COM KKL 409.1 OBD2"
- With the engine running, click the "Cruise Control" tab in the engine diagnostics of FreeSSM.
- If you use FreeSSM to look at the Cruise Control codes with the car "on" but without the motor "running", it will display only C0043, which is a bogus code. It's the "cancel code" for when the ABS/VDC module isn't responsive. It means nothing so ignore it.
So anyways, using FreeSSM with the vehicle's motor running I was able to pull C0023. I found a list of ABS/VDC C**** trouble codes somewhere on the net. I attached it here for reference:
This code pointed to the front left (drivers side) ABS wheel speed sensor. Great! That seemed like a simple fix. I decided to take a look at the speed sensor and the condition of the wiring. As I pulled the sensor out of the hub, I noticed it was all chewed up and missing chunks. The damage on the sensor was caused by the magnetic tone encoder ring on the back of the hub assembly.
Well that seemed like an obvious root cause. I ordered a new hub assembly and speed sensor, and I installed them. WRONG. It didn't fix it! I made a rookie mistake on not properly diagnosing the issue and throwing parts at it!
At this point, I found the FSM section on diagnosing Code 0023. It had me test the voltage going to the speed sensor (+12V one pin, GND on the other pin). I ohm'ed out the wiring through the various connectors on their way to the ABS/VDC module. All seemed good.
I guess the last remaining step was to replace the ABS/VDC module in the engine bay. I knew it had to be this module as the main ECU was talking properly to the ABS/VDC unit (via canbus) and no other errors were present. So I went to the local pick-n-pull and grabbed the ABS/VDC module for $45. Before bothering to remove all the hard brake lines into the old module, I simply plugged the cable harness into the new junkyard unit. Well, the error code immediately went away! I cleared out the codes and they never came back.
So there you have it. One cause of wheel speed sensor issues can be a faulty ABS/VDC computer modules. It's easy to do a proper diagnosis without any fancy or expensive tools.