So every time it rains my 02 the speedometer starts to bounce. When it does this the speedo will fluctuate 10 20 30 mph. When it does this it will set a c0237 code which is the one that sets the check engine light. Also has a c0225 c0226 c0227 code. One of these is the driver front speed sensor for sure the wire on the speed sensor side is messed up. Any normal day if you hit a bump in the road it sets a abs light. Cycle the ignition and it will be gone till you hit another bump hubs are fine. The trans code will be a p0721 code and of course a p0700 code. Once the c0237 code is set and the speedo starts to bounce it gets hung in a gear. The hard part I'm having is it the Ecbm causing this because it's getting wet or what truck run flawless when dry. tomorrow I'm taking all the wire loom off and check the wiring and connections. I had this issue a while back on this truck after it left me walking almost one rainy night. The wire extension for the tcase has a plug I cut it out and spliced the wires together of course with a good heat shrinks connection. Iv seen those give quite an it of issues with the rear speed sensor. Little history on truck bone stock lb7 360000 miles it's a crew cab dually of course 4wd. Obviously the front speed sensors don't cause this issue on the rear. Can the ebcm cause this or a nsbu switch cause this. It's kind of starting to piss me off a little bit at least I have an lbz to fall back on.
02 lb7 speedometer bouncing
- Thread starter JOHNMcDANIEL0322
- Start date
Is it going in limp mode? I know GM uses a rear speed sensor in the tcase for abs. If you get a range shift Inhibited your nsbu is bad but I don't think that would cause speed to fluctuate. Also, TCU can get wet I would unplug it and hit with air compressor and then electrical cleaner.
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Yeah P0721 is the one to go after here I believe. The other C0237 and others can set due to speed sensor code. The c0265 is for ebcm relay and usually relates to the ebcm module itself or ground at driver side frame rail by body mount. Circuits 821 and 822 are the ones that send VSS signal to TCM. This is the rear output speed sensor on trans. Only ways I've gone about diagnosing this is with a meter and measuring to see if I'm losing the A/C hertz signal from sensor to TCM.
Sorry guys I just looked back on here. I found not only the plug had water in it for tcase extension wire, but also two wires that came from the main trans harness that goes around the back of the trans pan had chaffed on the wire loom. This loom ties into another loom which actually goes to the rear speed sensor. I cut it all out last night and re loomed it works excellent now trans shifts great again. The two wires that were chaffed was a purple and green wire they were twisted together as all the speed sensor wires are. I cut and heat shrieked it all back along with electrical tape to make sure it doesn't happen again.