Help with ABS errors

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gothicsera

OBS Enthusiast
Joined
Jul 10, 2016
Messages
77
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36
Location
Norfolk, England
My ABS light was on erratically, but now it's staying on. I pulled the codes this morning and got loads....

It's a '95 K2500.

21 - RF speed sensor/circuit open
22 - Missing RF speed signal
25 - LF speed sensor/circuit open
35 - VSS circuit open
66 - Open/shorted pump relay
73 - Memory error
86 - Shorted ABS indicator lamp

There's so many codes there I don't really know where to start! When I short the pins on the diagnostic connector I can hear the ABS pump run for 2 seconds.

Help!
 

VCaddy

I'm Awesome
Joined
Oct 30, 2014
Messages
140
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21
Location
Velva, ND
I'd try a set of wheel speed sensors, they're not expensive. Or at least check the connections and clean the current ones. That should take care of 21, 22, and 25.

Is this a 4L60E transmission? The PCM uses the VSS signal to shift, so does it shift fine and speedo work right?

73 sounds like a PROM error to me, not related to the ABS faults.
 
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