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 & VREF Wiring Harness Circuits
• Powertrain Control Module (PCM)

1. 1) Verify Operator Interaction
   
   DTC P0552 indicates PSP sensor circuit is open or 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 30 seconds of starting KOER ON-DEMAND SELF-TEST . If steering wheel was turned, go to next step. If steering wheel was not turned, repeat QUICK TEST .

2. 2) DTC P0552 & P0553: Check VREF Circuit Voltage
   
   Turn ignition switch to OFF position. Disconnect PSP sensor connector. Inspect connector for loose, damaged or corroded terminals. Repair as necessary. Turn ignition switch to ON position. Measure voltage between VREF terminal and SIG RTN terminal at PSP sensor harness connector. See Fig 1. If voltage is 4-6 volts, go to next step. If voltage is not 4-6 volts, go to TEST C .
   Fig 1: Identifying PSP Sensor Circuits & Connector Terminals (Escort)

   Courtesy of FORD MOTOR CO.
3. 3) Check PSP Sensor Operation
   
   Turn ignition switch to OFF position. Connect jumper wire to VREF circuit between PSP sensor and harness connector. See Fig 2. Connect jumper wire to SIG RTN circuit between PSP sensor and harness connector. Start engine and allow to idle. Measure voltage of PSP circuit between PSP sensor and ground. Turn steering wheel at least one-half turn right and left. If voltage is .3-4.7 volts, go to next step. If voltage is not .3-4.7 volts, replace PSP sensor.
   Fig 2: Testing PSP Sensor Operation

   Courtesy of FORD MOTOR CO.
4. 4) Check PSP Sensor Circuit Resistance
   
   Turn ignition switch to OFF position. Disconnect PCM connector(s). Inspect connector for loose, damaged or corroded terminals. Repair as necessary. Ensure PSP sensor is disconnected. Measure resistance of PSP sensor circuit between PSP sensor harness connector and PCM connector terminal No. 31. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open circuit.
5. 5) Check PSP Sensor Circuit For Short To Power
   
   Turn ignition switch to ON position. Measure voltage between chassis ground and PSP sensor harness connector PSP terminal. See Fig 1. If voltage is less than one volt, go to next step. If voltage is one volt or more, repair short to VPWR in PSP circuit.
6. 6) Check For Short To VREF, SIG RTN & Ground In Harness
   
   Measure resistance between PCM connector terminal No. 31 and terminals No. 90 and 91. Measure resistance between chassis ground and PSP circuit at PSP sensor harness connector. If all resistance readings are more than 10 k/ohms, replace PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. Program PCM. See FLASH VEHICLE IDENTIFICATION BLOCK PROCEDURE . If any resistance reading is 10 k/ohms or less, repair short circuit.
   NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 6) to step 10). No test procedures have been omitted.
7. 10) Continuous Memory DTC P0552 & P0553: Check For Intermittent Circuits To PSP Sensor
   
   Turn ignition switch to OFF position. Connect scan tool to DLC. Turn ignition switch to ON position. Using scan tool, select PPS PID from PID/DATA MONITOR & RECORD menu. Observe PSP PID voltage for indication of fault while shaking and bending PSP sensor wiring harness and connector. Tap lightly on PSP sensor to simulate road shock. An indication of fault is a sudden change in PSP PID voltage. If fault is indicated, isolate and repair as necessary. If no fault is indicated, go to TEST Z .