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Home >> Buick >> 1996 >> Roadmaster Base >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control Systems - Tests W/Codes >> Diagnostic Trouble Codes >> DTC P1652 - VSS Output Circuit >> Diagnostic Procedures

Diagnostic Procedures

  1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
    NOTE: Support the lower control arms so drive axles are in normal horizontal position or drive axles will be damaged.
  2. Turn ignition off. Raise drive wheel. Start engine. Disable ASR/TCS system (if equipped). Start engine and run at idle. Place transmission in gear. If speedometer indicates vehicle speed, see DIAGNOSTIC AIDS. If speedometer does not indicate vehicle speed, go to next step.
  3. Turn ignition off. Disconnect PCM connector C2. Install Signal Generator Tester (J 33431-B) to VSS output circuit of PCM harness connector and ground. Turn ignition on. Turn tester on and set tester to generate vehicle speed signal. If vehicle speedometer indicates vehicle speed, go to next step. If speedometer does not indicate vehicle speed, check speedometer assembly in instrument panel.
  4. Check for faulty PCM connections. Repair as necessary. After repairs, go to step 6). If connections are okay, go to next step.
  5. Replace PCM. Program replacement PCM using required equipment. After replacing PCM, go to next step.
  6. Using scan tool, select DTC, CLEAR INFO function. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, then enter DTC P1652. Operate vehicle within conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool did not indicate that this test ran and passed, repeat step 2).
  7. Using scan tool, select CAPTURE INFO, REVIEW INFO function. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.
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