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GM Tech (Cam)
GM Tech (Cam), Chevy Technician
Category: Chevy
Satisfied Customers: 15133
Experience:  GM Grand Master Technician 2007. 14 years experience.
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2007 Chevy Avalanche. ABS and traction dash lights on a

Customer Question

2007 Chevy Avalanche. ABS and traction dash lights on a couple of months ago. Used friends OBDC II w/ ABS code reader. Code encountered C0045. Replaced left rear speed sensor as it stated. Erased codes both lights still on. Still reading C0045. Had mechanic check wiring on left rear. No issues found. Ordered replacement sensor. Uncertain if that fix the problem. read possible causes Poor pin connection, spacing/alignment issue in axle tube clean access point, bad sensor, wire faulty, resistance AC 100-300 mV when wheel turned, diff fluid w/ metal, bad battery!? Interesting point, battery died unexpectedly a couple of weeks ago. Jumped and has been running fine. Battery hasn't been tested. Where should I look next? Thanks! John
JA: Have you checked the fuses? The dashboard bulbs?
Customer: Dashboard bulbs are working fine. Haven't checked fuses. Where?
JA: Are you hoping to fix this yourself? What have you tried so far?
Customer: Like to fix myself
JA: Anything else you think the mechanic should know?
Customer: can't think of anything else.
Submitted: 2 months ago.
Category: Chevy
Expert:  david craig replied 2 months ago.

Hi Im David, so the abs/trac lights are as you well know are generated by a few things. one being the wheel speed sensors of course. I see that when you spun the tire on the left rear it read 100-300 mv. that is too low of a reading. i know it depends on how fast you spin the tire but in order to be certain of the correct generated voltage, try spinning it faster to see if the ac voltage goes higher. it should get close to 500-700 mv

Customer: replied 2 months ago.
Hi David, I offered a detailed explanation of what I encountered to date and possible solutions that I found online that Iwas hoping to brainstorm with you. Was hoping for a more comprehensive response, be more engaging, asking questions to clarify, respond to my questions regarding replacing the speed sensor a second time... waste of time? Battery recent died, jumped, seems to be working fine, not tested, would replacing help? Curious, what does you gut tell you would be the next logical step/thing check/action to take, what are we looking for when doing so, etc. Other than spin the tire faster. Please advise. Thanks. John
Customer: replied 2 months ago.
To be clear, I didn't not check the mv. All info online pointed to simply replacing rear speed sensor. Was hoping it would be a quick/easy fix. Unfortunately, it didn't work. Just learned about all the other possible solutions yesterday before deciding to try this service.Hoping you can save time to take the next logical step to address this issue asap. Thanks. John
Expert:  david craig replied 2 months ago.

The wheel speed sensor (WSS) receives ignition voltage from the Electronic Brake Control Module (EBCM) and provides a DC square wave signal back to the module. As the wheel spins, the EBCM uses the frequency of the square wave signal to calculate the wheel speed, having said that take the vehicle for a spin with a abs capable scan tool and watch the wheel speed sensor outputs. if the left rear difference is more than 2mph then it is either a rust issue on that reluctor ring or a problem with the input to the ebcm

Expert:  david craig replied 2 months ago.

i offered a detailed description of what the problem could be. is that to your satisfaction or should i dig a bit deeper? let me know. im here for you

Customer: replied 2 months ago.
My investment in an OTC 9450 was approximately $150. I just contacted them to confirm that a device that offers the features/info you're requesting costs $2,500. Not an option. Need guidance and advice as a handyman. Not a pro with a shop. Don't have access to those resources aside from paying a mechanic to diagnose. That's what thought the service offered. Think I need to look at other options. Thanks. John
Customer: replied 2 months ago.
Expert:  Dan replied 2 months ago.

New expert here, would you like the repair procedures and diagrams for the C0045 from the factory service manual?

Customer: replied 2 months ago.
Hi Dan, please. That would be great.Can you see my initial question and dialogue? If so, would like to get your read on the situation and recommended next steps to quickly troubleshoot and resolve this problem. Appreciate your help. Thanks. John
Expert:  Dan replied 2 months ago.


Customer: replied 2 months ago.

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