long time problem: intermittent abs and brake lights on dashboard

Finally addressing this problem. the two front wheel speed sensors measure 1026 and 1032 ohms, which is the middle of the specs in Haynes for 1999 silverado 1500. others here have suggested cleaning the speed senors, so i'm heading back out to do just that.

 

dang, well, that is not going to happen today. looks like the wheel speed sensor is held on by an allen bolt that is blocked by the rotor, and i do not have what it'll take to remove the brake caliper.

i'm thinking of buying a scanner that will read the ABS system on a 1999 1500 2wd silverado. most seem to start with the 2000 model year. any suggestions? my preference would be for a laptop based scanner thinking it would be cheaper.

 

i'm thinking of getting a Actron CP9580 for $174 at Sears

the actron site flags it as a 'new' item and my 99 silvy is listed in the coverage chart:

http://actron.com/publish/2010/05/28/Chart_16364.pdf

anyone have this particular scanner?

 

the CP9580 Quick Test found 8 ABS codes:

B0237
B0265
B0245
B0251
B0252
B0241
B0242
B0246

 

the full text from the CP9580 scan tool is this:

B0237 Rear Speed Sensor Erratic HISTORY
B0265 Electronic Brake Control Module Motor Relay Circuit HISTORY
B0245 Electronic Brake Control Module HISTORY
B0251 Electronic Brake Control Module HISTORY
B0252 Electronic Brake Control Module HISTORY
B0241 Electronic Brake Control Module HISTORY
B0242 Electronic Brake Control Module HISTORY
B0246 Electronic Brake Control Module HISTORY

obd-codes.com lists these:

C0237 Rear Wheel Speed Signal Erratic
C0265 EBCM Relay Circuit
C0245 Wheel Speed Sensor Frequency Error
C0251 (not listed)
C0252 (not listed)
C0241 EBCM Control Valve Circuit
C0242 (not listed)
C0246 (not listed)


Autozone has a list of code definitions that are somewhat different compared to the list on odb-codes.com

http://www.autozone.com/autozone/rep...96b43f8025edb7

C0237 Rear Wheel Speed Signal Erratic
C0265 EBCM Relay Circuit
C0245 EBCM Control Valve Circuit
C0251 EBCM Control Valve Circuit
C0252 EBCM Control Valve Circuit
C0241 EBCM Control Valve Circuit
C0242 EBCM Control Valve Circuit
C0246 EBCM Control Valve Circuit



and thedieselgarage.com has probably the best list:

GM Diagnostic Trouble Code List part 1 - TheDieselGarage.com

C0237 Rear Wheel Speed Signal Circuit Erratic EBCM DTC C0235-C0237 or P0609
C0265 EBCM Motor Relay Circuit EBCM DTC C0265 or C0266 and C065 or C066
C0245 EBCM Control Valve Circuit EBCM DTC C0241-C0254 or C041-C054
C0251 EBCM Control Valve Circuit EBCM DTC C0241-C0254 or C041-C054
C0252 EBCM Control Valve Circuit EBCM DTC C0241-C0254 or C041-C054
C0241 EBCM Control Valve Circuit EBCM DTC C0241-C0254 or C041-C054
C0242 EBCM Control Valve Circuit EBCM DTC C0241-C0254 or C041-C054
C0246 EBCM Control Valve Circuit EBCM DTC C0241-C0254 or C041-C054


here is the Mitchels 1999 Sierra & Silverado page 8-396





and here is what a chiltons says:

 

earlier today i phoned in my VIN to the dealer, who said that there were no outstanding recalls on my truck

 

google search for the list of 8 'C' codes

and the results:

Help with CEL & ABS/Brake lights - 1999 Z71 - Chevrolet Forum - Chevy Enthusiasts Forums

I am trouleshooting an ABS system in a 2000 GMC K3500. I ... - JustAnswer

2001 Chevrolet Silverado Abs Brakes Problem

the JustAnswer page says this:

 

Here's what I got from Mitchel's OnDemand5:

C0237 REAR SPEED SENSOR SIGNAL ERRATIC
C0265 PUMP MOTOR RELAY CIRCUIT OPEN
C0245 LEFT FRONT ISOLATION SOLENOID CIRCUIT OPEN
C0251 REAR ISOLATION SOLENOID CIRCUIT OPEN
C0252 REAR DUMP SOLENOID CIRCUIT OPEN
C0241 RIGHT FRONT ISOLATION SOLENOID CIRCUIT OPEN
C0242 RIGHT FRONT DUMP SOLENOID CIRCUIT OPEN
C0246 LEFT FRONT DUMP SOLENOID CIRCUIT OPEN

If I were to take a stab at the problem here, I'd look for an ABS fuse/relay and start from there. Get some wiring schematics and figure out how the circuit works and start systematically checking different circuits.

Good luck.

 

My 98 was throwing 8 or 10 codes for abs awhile ago... unfortunately it was the EBCM that was throwing them all... and THEY'RE EXPENSIVE! I ended up taking it off, cleaning all the connections, and the light is staying offf

 

update: used the CP9580 this morning to erase the ABS codes, then took the truck on an 8 mi round trip errand. at the beginning the dash ABS + Brake lites were not lit up, as is always the case on ignition. scantool kept reporting zero ABS codes until two dash lights lit up about 2 miles later. from that point onward, scantool reported one and only one ABS code: C0265.

before heading home, i erased the code. dash lites were out. scantool again kept reporting zero ABS codes until the ABS + Brake dash lights lit up about 1 mile from home, at which point scantool began reporting one only one ABS code, C0265.

in regards to C0237, i should add that i've never noticed any problems with the speedometer, which is supposedly driven by the same Vehicle Speed Sensor referenced by that code.