Diagnostic Aids

Perform this test when directed by QUICK TEST  or other test procedures. This test is intended to diagnose the following:

• PSP sensor.
• PSP, SIG RTN and VREF wiring harness circuits.
• Powertrain Control Module (PCM).

Fig 1: PSP Sensor Test Circuit & Connector Terminals

1. Step 1) Verify Operator Interaction  DTC P0552 indicates PSP sensor circuit is shorted to ground. DTC P0553 indicates PSP sensor circuit is shorted to power. DTC P1550 indicates PSP sensor circuit is out of self-test range. Possible causes for this fault are:
   • Damaged PSP sensor.
   • Open or shorted SIG RTN circuit.
   • Open or shorted VREF circuit.
   • Open or shorted PSP sensor signal circuit.
   • Faulty Powertrain Control Module (PCM).

   Ensure steering wheel was turned at least 1/2 turn within 1-2 seconds after ID portion of test. If steering wheel was turned, go to next step. If steering wheel was not turned, repeat QUICK TEST .

2. Step 2) Check VREF Circuit Voltage  Turn ignition off. Disconnect PSP sensor connector. Inspect connector for damaged pins, corrosion and loose wires. Repair as necessary. Turn ignition on. Measure voltage between VREF circuit terminal and SIG RTN circuit terminal at PSP sensor wiring harness connector. If voltage is 4-6 volts, go to next step. If voltage is not 4-6 volts, go to CIRCUIT TEST C.
3. Step 3) Check PCM Response  Start engine and allow it to idle. Connect a jumper wire between VREF circuit terminal and PSP sensor circuit terminal at PSP sensor wiring harness connector. If engine speed increased, reconnect PSP sensor connector and go to next step. If engine speed did not increase, go to step 5).
4. Step 4) Check PSP Sensor Operation  Turn ignition off. Disconnect PCM 104-pin connector. Inspect connector for damaged pins, corrosion and loose wires. Repair as necessary. Install EEC-V Breakout Box (014-000950), leaving PCM connected. Start engine and allow it to idle. Connect voltmeter between test pins No. 31 and 91 at breakout box. Observe voltmeter and turn steering wheel all the way to the left then all the way to the right. If voltage changes from 0.5-4.5 volts, PSP circuit is functioning properly. Fault is intermittent. Go to CIRCUIT TEST Z. If voltage does not change from 0.5-4.5 volts, replace PSP sensor. Remove breakout box and repeat QUICK TEST .
5. Step 5) Check PSP Sensor Circuit Continuity  Turn ignition off. Disconnect PCM 104-pin connector. Inspect connector for damaged pins, corrosion and loose wires. Repair as necessary. Install EEC-V Breakout Box (014-000950), leaving PCM disconnected. Ensure PSP sensor is disconnected. Perform the following procedures:
   • Measure resistance between PSP sensor circuit terminal at PSP sensor wiring harness connector and test pin No. 31 at breakout box.
   • Measure resistance between VREF circuit terminal at PSP sensor wiring harness connector and test pin No. 90 at breakout box.
   • Measure resistance between SIG RTN circuit at PSP sensor wiring harness connector and test pin No. 91 at breakout box.

   If each reading is less than 5 ohms, go to next step. If any reading is 5 ohms or more, repair open circuit. Remove breakout box, reconnect all components and repeat QUICK TEST .

6. Step 6) Check For Short To Power Or Ground  Leave PCM and PSP sensor disconnected. Measure resistance between chassis ground and test pin No. 31, 90 and 91 at breakout box. If each reading is more than 10,000 ohms, replace PCM. Remove breakout box and repeat QUICK TEST . If any reading is 10,000 ohms or less, repair short to power or short to ground. Remove breakout box and repeat QUICK TEST .