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Programmable Speedometer/Odometer Module (PSOM) Test

CAUTION: Only the wiring harness end of connector should be probed.
  1. Turn ignition switch to RUN position. If anti-lock light on dash goes out after self-test, go to next step.
  2. If odometer display is on and digits appear normal, go to next step. If odometer display is not on or if digits are abnormal, go to step 6).
  3. If ERROR 3 appears in odometer display, go to SPEEDOMETER/ODOMETER TEST  . If the word ERROR appears, replace instrument cluster. See INSTRUMENT CLUSTER R & I  under REMOVAL & INSTALLATION. If neither word appears, go to next step.
  4. If odometer displays increments of mileage with vehicle in motion or rear wheels turning, go to step 9). If odometer does not give mileage, go to next step.
  5. If speedometer indication increases with increasing vehicle speed, replace instrument cluster. See, under REMOVAL & INSTALLATION, INSTRUMENT CLUSTER R & I  . If speedometer does not indicate increase, go to step 8).
  6. Remove, check and reinstall battery power fuses No. 8 and 17. See Figure . If fuses are blown, replace with NEW fuse(s). If new fuse blows, determine cause and repair as necessary. With fuses intact, if the speedometer and odometer operate properly, replace instrument cluster. See INSTRUMENT CLUSTER R & I  under REMOVAL & INSTALLATION. If speedometer and odometer do not work properly, go to next step.
  7. Probing only wiring harness end of connector, verify battery, ground and ignition on PSOM connector terminals No. 1, 2 and 3 respectively with ignition switch in RUN position. See Figure . If resistance to ground is less than one ohm with terminals in wiring harness connector completely seated in connector and locking tabs, replace instrument cluster. See INSTRUMENT CLUSTER R & I  under REMOVAL & INSTALLATION. If resistance is more than one ohm, repair wiring harness and fuses as required and verify operation.
  8. Using a voltmeter, connect to PSOM connector terminal No. 4 (+ speed signal input) and terminal No. 5 (- speed signal return). See Figure . If voltage increases smoothly and continuously from zero to about 3.5 volts and vehicle speed increases from zero to 30 MPH, replace instrument cluster. See INSTRUMENT CLUSTER R & I  under REMOVAL & INSTALLATION. If voltage does not increase smoothly, repair wiring (check for open or shorted wiring).
  9. If speedometer indication increases and decreases relative to vehicle speed, operation is normal. If operation is not normal, replace instrument cluster. See INSTRUMENT CLUSTER R & I  under REMOVAL & INSTALLATION.
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