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Tachometer Inaccurate

NOTE: Before proceeding with tachometer testing, check PCM for stored Diagnostic Trouble Codes (DTCs) and repair as necessary. See TESTS W/CODES article in ENGINE PERFORMANCE section.
  1. Turn ignition on. Check for voltage at output side of fuse No. 30 of interior fuse box. See Figure . If voltage is present, go to next step. If voltage is not present, replace fuse. and check operation. If fuse repeatedly blows check Purple wire for short to ground.
  2. Turn ignition switch to OFF position. Partially remove instrument panel. See INSTRUMENT CLUSTER  under REMOVAL & INSTALLATION. Turn ignition switch to RUN position. Check voltage at cluster connector C1, pin No. 9 (Purple wire). See Figure and Figure . If battery voltage is present, go to next step. If voltage is not present, repair open Purple wire.
  3. With ignition switch in OFF position, check resistance between cluster connector C1, pin No. 13 (Black wire) and ground. If resistance is 5 ohms or less, go to next step. If resistance is more than 5 ohms, repair circuit No. 31 (Black wire) for open and check operation.
  4. Turn ignition switch to OFF position. Disconnect cluster connector C1. Disconnect powertrain control module. Install 104-pin breakout box. Measure resistance of circuit No. 8 (White/Black wire) between powertrain control module, pin No. 48 on breakout box and cluster connector C1, pin No. 8 (White/Black wire). If resistance is 5 ohms or less, go to next step. If resistance is more than 5 ohms, repair open White/Black wire and check operation.
  5. Check resistance from tachometer connector clips to instrument cluster printed circuit. If resistance is less than 5 ohms, go to next step. If resistance is more than 5 ohms, replace connector clips and check operation.
  6. With ignition switch in OFF position, check continuity from tachometer connector clips to cluster connector C1, pins No. 8 (White/Black wire), No. 9 (Purple wire) and No. 13 (Black wire). If resistance is less than 5 ohms, replace tachometer and retest system. See TACHOMETER  under REMOVAL & INSTALLATION. If resistance is more than 5 ohms, replace instrument cluster printed circuit board. See PRINTED CIRCUIT  under REMOVAL & INSTALLATION.
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