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Dan, Technician
Category: Chevy
Satisfied Customers: 24580
Experience:  Independent Shop Experience, 2 Year Automotive Diploma, & Access to Information Database
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Chevrolet Tahoe 4x4: 2002 Tahoe "service 4wd" light came on It

Customer Question

2002 Tahoe "service 4wd" light came on
It was OK when I parked the truck, then came on when I re-started it about 4 hrs. later. No indicator lights come on in the selector panel, and the unit does not appear to be shifting. Checked the transfer case and 4wd fuses-both good OBD reader shows nothing????

Submitted: 5 years ago.
Category: Chevy
Expert:  Dan replied 5 years ago.
Welcome to JustAnswer, my name is Dan and I'm here to help get your problem resolved. The most common cause of this code is a failed 4WD Engage Switch which sets code B2725. If light has only came on once and no codes were set I'd leave it alone for now, then next time light comes on if it does check them again. If code B2725 comes back replace the Engage Switch. Let me know if you have any questions, thanks.
Customer: replied 5 years ago.
The light is staying on all the time. I found no codes on the reader. Roy
Expert:  Dan replied 5 years ago.
Thanks for update, is 4x4 working correctly?
Customer: replied 5 years ago.
It does not appear to be working at all. I haven't really tried it hard in loose surfaces. When the light first came on, it felt like the Xfer case was trying to shift at random, but that has now stopped. I've only put about 20 miles on it since the light came on.
Expert:  Dan replied 5 years ago.

Does your scantool only read PCM (P-codes) or does it real all codes such as BCM (B-codes) ? If light is on and something isnt working there should be a code being set.

Customer: replied 5 years ago.
Actually, I'm not sure. It has a setting to read some kind of "flash(?) codes. The reader is at my lube shop, and I'm at home :-( Roy
Expert:  Dan replied 5 years ago.
Will you have codes checked and let me know what they are? There should be a code set and I would still think its probably related to engage switch as they are very common to fail and there is a updated part for them. Let me know, thanks.
Customer: replied 5 years ago.
I called my shop and talked to one of my techs and he said our reader only reads the PCM codes. Can I get back to you? Roy
Expert:  Dan replied 5 years ago.
Yes you can get back to me at any time, you will need to have a scantool capable of reading Non PCM codes hooked up to check codes. Let me know how it goes or if you run into questions, Thanks Roy.