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Test E: Incorrect Tachometer Reading

NOTE: This test applies to ZX2 models only.
  1. Using scan tool, observe RPM Parameter Identification (PID) and RPM readings over a range of engine speeds and compare to tachometer reading. If tachometer reading does not match scan tool readings, go to next step. If RPM PID does not match RPM reading, repair Clean Tach Output (CTO) circuit concern. See appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE. Retest system operation. If RPM PID, RPM and tachometer readings match, vehicle is okay.
  2. Turn ignition switch to LOCK position. Remove instrument cluster. See INSTRUMENT CLUSTER  under REMOVAL & INSTALLATION. Disconnect White instrument cluster 12-pin harness connector C258. See Figure. Turn ignition switch to ON position. Measure voltage between ground and White instrument cluster 12-pin harness connector C258 terminal No. 4 (Black/Yellow wire). If voltage is more than 10 volts, go to next step. If voltage is less than 10 volts, repair open in Black/Yellow wire. See WIRING DIAGRAMS . Retest system operation.
  3. Turn ignition switch to LOCK position. Measure resistance between ground and White instrument cluster 12-pin harness connector C258 terminal No. 6 (Black/Green wire). If resistance is less than 5 ohms, go to next step. If resistance is more than 5 ohms, repair open in Black/Green wire. See WIRING DIAGRAMS . Retest system operation.
  4. Visually inspect instrument cluster printed circuit for damage, cracks or hot spots. If instrument cluster printed circuit appears okay, go to next step. If instrument cluster printed circuit appears damaged, replace printed circuit and gauge contact clips. See PRINTED CIRCUIT  under REMOVAL & INSTALLATION. Retest system operation.
  5. Install EEC-V 104-pin Breakout Box (014-00950) following manufacturer's instructions. Measure resistance between breakout box terminal No. 48 and White instrument cluster 12-pin harness connector C258 terminal No. 5 (Light Green/Red wire). Resistance should be less than 5 ohms. Measure resistance between ground and White instrument cluster 12-pin harness connector C258 terminal No. 5 (Light Green/Red wire). Resistance should be more than 10 k/ohms. If both resistances are as specified, install new Powertrain Control Module (PCM). See appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE. Retest system operation. If resistances are not as specified, repair open or short to ground in Light Green/Red wire. See WIRING DIAGRAMS . Retest system operation.
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