Mechanics

CHEVY SPEEDODOMETER/OIL PRESSURE GAUGES

1991 Chevrolet S-10

Electrical problem
1991 Chevy S-10 4 cyl Two Wheel Drive Automatic

I just bought a 91 s10 for my son. The speedodometer intermittently works and the oil pressure gauge when driving is at 80. the truck run pretty good for being that old. I have changed the speed sensor (which still leaks trans fluid through the plug) and that didn't help. I was told to it could be the DRAC/speed buffer (I have no idea what or where it is) or the ground from the DRAC to the ECM. I need help...I am no mechanic!! I believe I changed Brake module (what I thought was the DRAC/buffer) due to the p-brake light staying on. Well that p-brake light is fixed. Please let me know if you can help me. The pic. is what I changed.


http://www.2carpros.com/forum/automotive_pictures/321937_022209_2006_1.jpg

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Incubus75
February 22, 2009.




Thats the rear anti-lock control unit. The DRAC is under the right side of the dash next to the ECM.


http://www.2carpros.com/forum/automotive_pictures/62217_drac_1.jpg

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Merlin2021
Feb 23, 2009.
And that the drac was next to the ecm. I was told that it might be the ground from the drac to the ecm. I have no idea where the wire is. Looking a a Haynes book I see the wiring diagram that goes from the speed sensor(ppl& w/grn& blk) to the drac then to the speedodometer then to the ecm. I dont know what to do. I hear kind of a winding noise from the instrument cluster but I am not sure if its there when the sppedodo is working. Any suggestions on what I should do?

Tiny
Incubus75
Feb 23, 2009.
VEHICLE SPEED SENSOR & DIGITAL RATIO ADAPTER CONTROLLER (DRAC) TESTING Speedometer & Odometer Are Inaccurate Ensure that correct digital ratio adapter controller is installed for specific final drive ratio. Replace if necessary. Speedometer & Odometer Do Not Operate Properly 1. Disconnect Digital Ratio Adapter Controller (DRAC). Turn ignition on. Measure voltage between Pink/Black wire of DRAC harness connector and good chassis ground. 2. If battery voltage is present, go to next step. If voltage is less than battery voltage, check for blown BRAKE fuse and replace if necessary. If fuse is okay, check for an open or short in Pink/Black wire between fuse block and DRAC harness connector. Repair as necessary. 3. On Astro and Safari, measure voltage between Pink/Black wire terminal and Black/White wire terminal of DRAC harness connector. If battery voltage is present, go to step 5). If battery voltage is not present, check for open or short in Black/White wire and repair as necessary. 4. On " S" and " T" Series, measure voltage between Light Blue/Black wire terminal and Black wire terminal of DRAC harness connector. If battery voltage is present, go to next step. If battery voltage is not present, check for open or short in Black wire and repair as necessary. 5. Raise and support vehicle. Start engine and place transmission in Drive. Measure voltage between Purple/White wire terminal and Light Green/Black wire terminal of DRAC harness connector. 6. If voltage is present, go to next step. If voltage is not present, check both wires for shorts or opens and repair as necessary. If wires are okay, replace vehicle speed sensor. 7. With vehicle still raised, engine running and transmission in Drive, connect DRAC harness connector to digital ratio adapter controller. Backprobe DRAC harness connector and measure voltage changes between Pink/Black wire terminal (Light Blue/Black wire terminal on " S" and " T" Series) and Black/White wire terminal (Black wire terminal on " S" and " T" Series) while varying vehicle speed. 8. If voltage does not change with vehicle speed, go to next step. If voltage varies with vehicle speed, replace DRAC. 9. Measure voltage between DRAC harness connector Yellow wire terminal and Black/White wire terminal (Black wire terminal on " S" and " T" Series) while varying vehicle speed. 10. If voltage does not vary with vehicle speed, test instrument cluster. See appropriate ELECTRONIC INSTRUMENT CLUSTER TESTING. If voltage varies with vehicle speed, replace DRAC. Page 1 of 1 INSTRUMENT PANEL (EXCEPT SYCLONE) -1991 Chevrolet S10 Pickup 2/26/2009 If it is the Digital Ratio Adapter Controller, remove the negative battery cable before replacing it.
If the VSS is leaking, it's cracked and should be changed again! Or the tranny housing has a crack, have it looked at.

Merlin2021
Feb 26, 2009.

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