DTC P0501: VEHICLE SPEED SIGNAL RATIONALITY
Monitor & Set Conditions
Vehicle Speed Sensor (VSS) signal is monitored when no VSS DTCs or Chrysler Collision Detection (CCD) errors are set. DTC may be stored when CCD vehicle speed indicates greater than 20 MPH for 2 seconds, ECM vehicle speed indicates less than 10 MPH and PCM does not receive a VSS signal from Controller Anti-Lock Brake (CAB) module.
Possible Causes
- CAB DTC
- CAB
- Vehicle Speed Signal Shorted To Voltage
- Vehicle Speed Signal Shorted To Ground
- Vehicle Speed Signal Open From CAB To PCM
- ECM
- PCM
Testing
1. Turn ignition on. Using DRBIII(R) scan tool, check for wheel speed sensor codes set in CAB module. If no wheel speed sensor DTCs exist, go to next step. If any wheel speed sensor DTCs exist, perform test procedures for CAB module DTCs. See appropriate ANTI-LOCK article in BRAKES.
2. Turn ignition off. Disconnect Black 14-pin CAB module harness connector C1. CAB module is located near Power Distribution Center (PDC) at driver's side of engine compartment. Turn ignition on. Connect one end of jumper wire to terminal No. 12 (White/Orange wire) on 14-pin CAB module harness connector C1. Using scan tool, select PCM and monitor vehicle speed sensor signal while intermittently grounding the other end of the jumper wire at a rapid rate. If scan tool displays zero MPH, go to next step. If scan tool displays greater than zero MPH, replace and program CAB module. See appropriate ANTILOCK article in BRAKES.
3. Remove jumper wire. Ensure ignition is on. Using DVOM, measure voltage between ground and terminal No. 12 (White/Orange wire) on 14-pin CAB module harness connector C1. If voltage is not 4-6 volts, go to next step. If voltage is 4-6 volts, test is complete.
4. Turn ignition off. Ensure CAB module harness connector C1 is still disconnected. Disconnect ECM harness connector. ECM is located on driver's side of engine, just in front of fuel transfer pump and contains a 50-pin connector. Turn ignition on. Using DVOM, measure voltage between ground and terminal No. 12 (White/Orange wire) on 14-pin CAB module harness connector C1. If voltage is not 4-6 volts, go to next step. If voltage is 4-6 volts, replace and program ECM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article.
5. Turn ignition off. Ensure CAB module harness connector C1 and ECM harness connector are still disconnected. Disconnect PCM harness connectors. Turn ignition on. Using DVOM, measure voltage between ground and terminal No. 12 (White/Orange wire) on 14-pin CAB module harness connector C1. If voltage is one volt or less, go to next step. If voltage is greater than one volt, repair short to voltage in White/Orange wire between CAB, ECM and PCM.
6. Ensure ignition is on. Ensure CAB module harness connector C1, ECM harness connector and PCM harness connectors are still disconnected. Using DVOM, measure resistance between ground and terminal No. 12 (White/Orange wire) on 14-pin CAB module connector C1. If resistance is 100 ohms or greater, go to next step. If resistance is less than 100 ohms, repair short to ground in White/Orange wire.
7. Ensure ignition is on. Ensure CAB module harness connector C1, ECM harness connector and PCM harness connectors are still disconnected. Using DVOM, measure resistance of White/Orange wire between terminal No. 12 on 14-pin CAB module connector C1 and terminal No. 27 on PCM connector C2. If resistance is less than 5 ohms, test is complete. If resistance is 5 ohms or greater, repair open in White/Orange wire.