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Ron, ASE Certified Technician
Category: Chevy
Satisfied Customers: 35490
Experience:  35 years experience with ASE Certs
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Need an expert opinion, I’m not a mechanic, handy man...

Customer Question

Need an expert opinion, I’m not a mechanic, handy man... 2007 Chevy Avalanche LTZ 4WD with 105k. ABS and traction dash lights came on a couple of months ago. Vehicle drives fine. Used a friends OTC 9450 $150 OBDC II (doesn’t have ability to read in real time speed sensor values) w/ ABS code reader. Code encountered C0045. Replaced left rear speed sensor as it stated. Pretty straight forward replacement. Erased codes both lights are still on. Still reading C0045.Had mechanic check wiring on left rear wheel by sensor. No issues found. Ordered another replacement sensor. What is the likelihood that will fix the problem?Could you provide a copy of the Chevy repair procedures and diagrams for the C0045 from the factory service manual and would that help?Before posting my question here, did some preliminary research online from an number of Chevy forums. Read possible causes could be... Poor pin connection, spacing/alignment issue in axle tube clean/sand access point, bad sensor, faulty wire, diff fluid has metal in it, even a bad battery.Interesting point, battery died unexpectedly a couple of weeks ago. Lights were already on before. We jumped it and has been running fine. Battery hasn't been tested. Please let me know if you have any questions to help clarify the situation/problem. Where should I look next? Hoping you can me save time to take the next logical step to address this issue asap.Thanks.John
Submitted: 11 months ago.
Category: Chevy
Expert:  Ron replied 11 months ago.

Hello John, my name is ***** ***** I am a professional here at Justanswer. Thank you for your question and I will assist you with your concern.

It highly unlikely you have two bad wheel speed sensor so I would suspect you have a wiring concern as well. I have enclosed the test steps in the link below for checking the LR speed sensor circuit as well as the wiring diagram. Have a look and see if this will help you determine the cause and get this resolved. See the test steps in the first link and the wiring diagrams in the second two links.

Customer: replied 11 months ago.
Hi Ron, appreciate the details. To be honest, I'm a little out of my depth using a multimeter. I have one, however, never really used it to test omh's, mv, etc. before.Step one, assuming second lead would be grounded to frame to determine value?
#3, uncertain how to determine open or short circuit
#4, build jumper wire, via EBCM connect terminal Battery B #25 to 21 LR WHL SNS. Then buy a resister, etc.
What is the consequence if done incorrectly?Thinking it may be best to leave this to the pros. Curious, if not the sensor and wire is intact then EBCM would need to be replaced. I that the idea and what id the likelihood its that given the age and miles?Please advise.Thanks,John
Expert:  Ron replied 11 months ago.

John, since you have replaced the sensor then I suspect your dealing with either a wiring concern or the EBCM is at fault. It would also be a lot easier if your scan tool could read the data stream to see if the sensor signal is reading. If your not comfortable doing the testing then its is likely best left to someone who is. If the follow the enclosed steps it should be fairly easy to nail it down. At either rate, Im here if need be. Thank you as well.

Customer: replied 11 months ago.
Good morning Ron,Agreed. I've been told devices that offer real-time WSS data stream info run close to $2500. My $150 OTC will not work.Perhaps willing to give it a try. Easier to field replacement w/ ability to return part. That said, Curious, if not the sensor given that it's been replace, and the age and mileage what is the likelihood its the EBCM ($150 to replace)?Please clarify step #4. disconnect cable to EBCM unit, build jumper wire, then use to connect terminal Battery B #25 to LR WHL SNS #21? How would resister be used and what is the consequence if jump cable not used correctly? Youtube video available to learn process?Thanks!John
Expert:  Ron replied 11 months ago.

John Its very likely the EBCM is at fault if the wiring checks okay to it. I would at least check that before replacing any parts. A Jumper is simply that, your going to jump battery power from a 12 volt source . Your checking to see if the new sensor is sending a signal. The steps are pretty self explanatory. Unfortunately I do not have a video to share with you. If this is not something your comfortable doing I would seek out some help with some one who is.