Vehicle Speed Signal Malfunction

DTC P0500, P0501, P1502 DETECTION CONDITION AND POSSIBLE

DTC P0500, P0501, P1502	VEHICLE SPEED SIGNAL MALFUNCTION
DETECTION CONDITION	P0500 (MIL triggered), P0501 (MIL not triggered) and P1502 (flash TCIL) indicate that the PCM has detected an error in the vehicle speed information received from the ABS control module, GEM module or CTM module.
POSSIBLE CAUSE	Damaged ABS control module. Damaged ABS wheel speed sensors. Damaged ABS wheel speed sensor harness circuits. Open in ABS control module to PCM harness circuits. Short to ground in ABS control module to PCM harness circuits. Damaged PCM. Open in VSS+/VSS- harness circuit. Short to GND in VSS harness circuit. Short to PWR in VSS harness circuit. Open or short in the vehicle speed circuit(s) (VSC) between the PCM and appropriate control module. Damaged wheel speed sensor harness circuit(s). Damage in module(s) connected to VSS/VSS circuit.
HINT	VSS Description Variable reluctance or Hall-effect sensor. Generates a waveform with a frequency that is proportional to the speed of the vehicle. The lower the speed, the lower the frequency. The higher the speed, the higher the frequency. The PCM uses the frequency signal to control such parameters as fuel injection, ignition control, transmission shift scheduling and torque converter clutch scheduling.
Courtesy of MAZDA MOTORS CORP.
Courtesy of MAZDA MOTORS CORP.

DTC P0500, P0501, P1502 INSPECTION

STEP	INSPECTION		ACTION
1	Was PCM Quick Test performed?	Yes	Go to next step.
1	Was PCM Quick Test performed?	No	Perform PCM Quick Test.
2	DTC P0500/P0501/P1502: CHECK VEHICLE SPEED PID NOTE: On 4WABS, the VSS signal to the PCM comes from the ABS unit and on RWABS, the signal comes from the GEM or CTM. Key ON, Engine Running (KOER). Access VSS PID with NGS Tester. Obeying all local traffic laws, complete the following: Take the vehicle to a suitable location and gradually increase the vehicle speed to 80 km/h (50 mph), while observing the VSS PID mph values. Did the VSS PID value match the speed at which you were traveling?	Yes	Key OFF. The VSS PID value was as expected. The fault that produced DTC is intermittent. Go to step 6.
2		No	Key OFF. The VSS PID value was not as expected. Go to next step.
3	CHECK VSS FOR SHORT TO POWER IN HARNESS Disconnect PCM. Install Breakout Box, leave PCM disconnected. Disconnect appropriate control module (ABS, 4WABS, RABS, GEM, or CTM). Key ON, Engine Running (KOER). Measure voltage of VSS SIG circuit between PCM test pin 58 and body ground. Key OFF. Was the voltage(s) less than 1.0 V?	Yes	Go to next step.
3		No	Repair short circuit. Go to step 8.
4	CHECK FOR OPEN VSS BETWEEN PCM AND CTM, GEM, OR ABS CONTROL MODULE Measure resistance of VSS SIG (VSS+) circuit between PCM test pin 58 and the appropriate control module connector. Is the resistance less than 5.0 ohms?	Yes	Go to next step.
4		No	Repair open circuit(s). Go to step 7.
5	CHECK VSS FOR SHORTS TO GROUND IN HARNESS Disconnect NGS Tester from DLC. Measure resistance of VSS SIG circuit between PCM test pin 58 and body ground. Is the resistance greater than 10K ohms?	Yes	Restore vehicle. See DIAGNOSIS & TESTING in Rear Anti-Lock Brake System article in Brakes or DIAGNOSIS & TESTING in Four Wheel Anti-Lock Brakes article in Brakes for further diagnosis of the ABS control module, its speed sensors and the speed sensor harness circuits. If those components are working properly, replace the PCM. Replace PCM. See COMPUTERIZED ENGINE CONTROLS . Go to step 7.
5		No	Repair short circuit. Go to step 8.
6	VISUAL INSPECTION Visually inspect the vehicle speed circuit harness circuits for any potential failures. Use the following check list for reference: Loose harness connection of vehicle speed circuits at the appropriate control module. Loose harness connection of vehicle speed circuits at the PCM. Incorrect harness routing of vehicle speed circuits. Did the visual inspection reveal any potential failure?	Yes	Repair fault as necessary. Go to step 7.
6		No	Unable to duplicate or identify fault at this time. See DIAGNOSIS & TESTING in Rear Anti-Lock Brake System article in Brakes or DIAGNOSIS & TESTING in Four Wheel Anti-Lock Brakes article in Brakes for diagnosis of intermittent control module and speed sensor concern.
7	VSS REPAIR VERIFICATION DRIVE CYCLE Warm engine to operating temperature. Complete the VSS Repair Verification Drive Cycle at least three times as described below: AUTOMATIC TRANSMISSIONS: Place transmission range selector lever in DRIVE range. Obey all local traffic laws. Accelerate heavily to 56 km/h (35 mph). Coast down to an idle and stop the vehicle. Shut the engine off. After the drive cycle is completed, retrieve any Continuous Memory DTCs. MANUAL TRANSMISSIONS: Shift to second from first gear. Obey all local traffic laws. Accelerate moderately to 64 km/h (40 mph). Coast down to an idle and stop the vehicle. After the drive cycle is completed, retrieve any Continuous Memory DTCs. Were any Continuous Memory DTCs generated during the drive cycle?	Yes	Testing is not complete. The repair has not been verified. Repair DTC(s).
7		No	Testing is complete. The repair has been verified. Go to step 8.
8	VERIFY TROUBLESHOOTING OF DTCs COMPLETED Make sure to reconnect all disconnected connectors. Clear DTCs from PCM memory using NGS tester generic OBD-II function. Perform PCM Quick Test. Is same DTC present?	Yes	Replace PCM. See COMPUTERIZED ENGINE CONTROLS . Repeat PCM Quick Test.
8		No	If any other DTC is present, go to applicable DTC inspection. If no DTC is present, troubleshooting complete.