95 S-10 ABS light on

CP

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#1
Make
Chevy
Model
S-10
Year
1995
Miles
95000
Engine
4.3
This one is a manual transmission with a 4.3 and 4 wheel drive. Has the OBD II connector port. Tried 2 scanners and both say “ no communication “. Checked power and grounds to the VCM above the coolant reservoir and they are good. I know I have one front wheel sensor bad. But before I fix the sensor, I wanted to know if the ABS system could communicate and tell me codes etc. Looking for someone who may be familiar with this system. Or is this one that may not communicate with my Modis or OTC scanner???
Thanks
 
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#2
there was a rare OBD system used @ this time. In the trade its referred to as OBD 1.5 google that and see if that is yuor scanner issue.
 

billr

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#3
If one of your scanners will connect to GM OBD1, then this should be doable. That "1.5" is OBD1 com coming out an OBD2 connector. You can make an adapter to convert the OBD2 port in the car to the OBD1 plug on the scanner cable; it takes just a few wires
 

grcauto

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#5
Your modis or otc should communicate if you have the software. Check the power and ground at the DLC. I think the DLC uses the cig lighter for power. If the cigar lighter don't work you likely need to replace it fuse and then your DLC should work.
 

CP

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Your modis or otc should communicate if you have the software. Check the power and ground at the DLC. I think the DLC uses the cig lighter for power. If the cigar lighter don't work you likely need to replace it fuse and then your DLC should work.
Forgot to mention that I can get data etc on the engine side of either scanner. There are 5 wires coming into the OBD plug. I’ll check into that info on the OBD 1.5 tomorrow
Thanks for now
 

grcauto

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#7
Forgot to mention that I can get data etc on the engine side of either scanner. There are 5 wires coming into the OBD plug. I’ll check into that info on the OBD 1.5 tomorrow
Thanks for now
Do you have the ABS software?
 

CP

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#8
Do you have the ABS software?
What do you mean by ABS software? I just have what is in my scanners?? Maybe there is something more I should know about? My scanners will read ABS on other vehicles
What more I have checked since last writing here, is.... checked the resistance at the plug of the VCM for the front sensors, and the vehicle speed sensor, rechecked power and grounds, tried grounding the wire at the OBD 2 port,this wire goes to the VCM and is a “diagnostic test “ wire (White/Black and #6 of the OBD 2 connector) trying to see if it would do a flash code. Wouldn’t flash anything. The ABS light comes on at start up, then goes off for a second and comes back on and stays on. So I haven’t accomplished anything yet as far as progress in knowing what the computer is seeing and don’t like and is turning on the light? Thanks for any help or advice is solving this one??
 
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#9
Does your truck also have an OBD1 connector?
1555730046746.png
To obtain the fault codes for the ABS brakes with a GM OBD1 system (and probably OBD1.5), ground pin H of the ALDL. Pin A of the ALDL is a ground pin, so pins A and H can be ‘jumped’.

Turn ignition ON but do not start the engine. The Anti-lock lamp will come on for four seconds, and then blink the 1-2 code followed by each stored trouble code. A 1-2 code is not a fault code; it indicates proper operation of the system. All codes are two digits. If you cannot extract codes this way, you might have a significant problem and MUST diagnose with the proper scan tool.

Codes will auto clear after 100 ignition cycles with no code set. You can clear most codes by jumping pin H to pin A with the ignition off. Turn Ignition on, wait approx. 4 seconds for lamp to go out then disconnect ground link, wait about 1 second, put link back, wait 1 second, remove link and so on three times, slowly, but within 10 seconds.
OBD1.5 CODES:
CODE 21 - FRONT RIGHT SENSOR CIRCUIT OPEN/SHORTED
CODE 22 - INTERMITTENT SIGNAL, FRONT RIGHT SENSOR
CODE 23 - MISSING SIGNAL, FRONT RIGHT SENSOR
CODE 24 - NOT USED
CODE 25 - FRONT LEFT SENSOR CIRCUIT OPEN/SHORTED
CODE 26 - INTERMITTENT SIGNAL, FRONT LEFT SENSOR
CODE 27 - MISSING SIGNAL, FRONT LEFT SENSOR
CODE 28 - NOT USED
CODE 31 - REAR RIGHT SENSOR CIRCUIT OPEN/SHORTED
CODE 32 - INTERMITTENT SIGNAL, RIGHT REAR SENSOR
CODE 33 - MISSING SIGNAL, REAR RIGHT SENSOR
CODE 34 - NOT USED
CODE 35 - REAR LEFT SENSOR CIRCUIT OPEN/SHORTED
CODE 36 - INTERMITTENT SIGNAL, REAR LEFT SENSOR
CODE 37 - MISSING SIGNAL, REAR LEFT SENSOR
CODE 38 - NOT USED
CODE 41 - ELECTRICAL DISTURBANCE INLET VALVE (CIRCUIT - FRONT RIGHT)
CODE 42 - ELECTRICAL DISTURBANCE OUTLET VALVE (CIRCUIT - FRONT RIGHT)
CODE 44 - ELECTRICAL DISTURBANCE ISOLATION VALVE SV1 (CIRCUIT - FRONT LEFT)
NOTE: TCS ONLY
CODE 44 - NOT USED
CODE 45 - ELECTRICAL DISTURBANCE INLET VALVE (CIRCUIT - FRONT LEFT)
CODE 46 - ELECTRICAL DISTURBANCE OUTLET VALVE (CIRCUIT - FRONT LEFT)
CODE 48 - ELECTRICAL DISTURBANCE ISOLATION VALVE SV2 (CIRCUIT -FRONT RIGHT)
NOTE: TCS ONLY
CODE 49 - NOT USED
CODE 51 - ELECTRICAL DISTURBANCE INLET VALVE (CIRCUIT - REAR RIGHT)
CODE 52 - ELECTRICAL DISTURBANCE OUTLET VALVE (CIRCUIT - REAR RIGHT)
CODE 55 - ELECTRICAL DISTURBANCE INLET VALVE (CIRCUIT - REAR LEFT)
CODE 56 - ELECTRICAL DISTURBANCE OUTLET VALVE (CIRCUIT - REAR LEFT)
CODE 62 - PUMP PRESSURE FAULT DURING ABS STOP
CODE 61 - PUMP MOTOR RUN FAULT
CODE 71 - CHECKSUM ERROR
CODE 72 - TRAVEL SWITCH INPUT NOT PROCESSABLE
CODE 73 - FLUID LEVEL SWITCH INPUT NOT PROCESSABLE
CODE 74 - PMV PRESSURE SWITCH CIRCUIT
NOTE: TCS ONLY
CODE 75 - PCM REQUESTED TCS DISABLE
NOTE: TCS ONLY
CODE 76 - UART SDL CIRCUIT/SIGNAL
CODE 77 - DELIVERED TORQUE PWM CIRCUIT/SIGNAL
NOTE: TCS ONLY
 

JP

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#10
You might be able to find a used Actron CP9449 ABS scanner used on the cheap. Got me through a lot of ABS-which-wheel-is-it? questions.
 

grcauto

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#11
What do you mean by ABS software? I just have what is in my scanners?? Maybe there is something more I should know about? My scanners will read ABS on other vehicles
What more I have checked since last writing here, is.... checked the resistance at the plug of the VCM for the front sensors, and the vehicle speed sensor, rechecked power and grounds, tried grounding the wire at the OBD 2 port,this wire goes to the VCM and is a “diagnostic test “ wire (White/Black and #6 of the OBD 2 connector) trying to see if it would do a flash code. Wouldn’t flash anything. The ABS light comes on at start up, then goes off for a second and comes back on and stays on. So I haven’t accomplished anything yet as far as progress in knowing what the computer is seeing and don’t like and is turning on the light? Thanks for any help or advice is solving this one??
Your 95 is a mutant. It would require OEM level software to talk with the ABS module. I have looked it up and if you have the VCM you also have the 16 pin DLC and therefore you MUST have the proper scan tool to communicate with the module. It will NOT flash codes.
 
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CP

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#12
yes this pickup has the 16 pin OBD2 connector and I don’t see a second connector. I have one more code reader that I forgot about that I’ll try tomorrow. Otherwise I may have to find another VCM to try. Always a possibility that something had gone wrong with it??? That the light stays on. Seems I’ve checked all the inputs and everything seems right.
 

billr

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#13
What cavities of that 16-pin connector housing have contacts in them?

I have no opinion right now as to the accuracy of the below, but think it is worth reading and considering:
http://www.imhdd.ms11.net/OLDS/obd.html

Another site that may have useful info. Note the long list there of links to other sources of OBD info:
http://aldlcable.com/
 
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#14
1555906995802.png
Does your truck have a Tan wire with White tracer at pin position 12 in the OBD2 connector? 1555907982111.png
 
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grcauto

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#15
yes this pickup has the 16 pin OBD2 connector and I don’t see a second connector. I have one more code reader that I forgot about that I’ll try tomorrow. Otherwise I may have to find another VCM to try. Always a possibility that something had gone wrong with it??? That the light stays on. Seems I’ve checked all the inputs and everything seems right.
More than likely it's NOT the VCM. A wheel sensor is much more common problem. If you do not get a scan tool to communicate with the module you'll likely save money by having a good local shop do the job. If you want wiring diagrams I have them.
BTW you say there's a bad front wheel sensor......that could be the whole problem.