Diagnostic Aids
Perform this test when instructed during QUICK TEST or if directed by other test procedures. Some vehicles may not have power steering, but PCM may be equipped with PSP switch software strategy. If a KOEO DTC P1650 or P1651 is displayed, check if vehicle is equipped with power steering. If vehicle is not equipped with power steering, disregard DTC P1650 or P1651. This test is only intended to diagnose:
- PSP Switch
- Wiring Harness Circuits (PSP & SIG RTN)
- Powertrain Control Module (PCM)
- 1) KOEO & KOER DTC P1650: Verify Electrical Function
When DTC P1650 is retrieved during KOEO ON-DEMAND SELF-TEST, this indicates PSP signal input to PCM is high. When DTC P1650 is retrieved during KOER ON-DEMAND SELF-TEST, this indicates PSP signal input to PCM did not change state. Possible causes for these faults are:- Steering Wheel Was Not Turned During KOER ON-DEMAND SELF-TEST
- Faulty PSP Switch/Shorting Bar Damage
- SIG RTN Circuit Open
- PSP Circuit Open Or Shorted To SIG RTN
- Faulty Powertrain Control Module (PCM)
Connect scan tool to Data Link Connector (DLC). Start engine and allow to idle. Using scan tool, select PSP PID from PID/DATA MONITOR & RECORD menu. Observe PSP/PSP V PID and turn steering wheel left, then right. If PSP/PSP V PID value does not indicate a change, go to next step. If PSP/PSP V PID value indicates a change, go to step 10).
- 2) Check For PSP Switch Cycling
Turn ignition switch to OFF position. Disconnect PSP switch harness connector or remove shorting bar. Install a jumper wire between PSP switch harness connector terminals. Start engine and allow to idle. Record PSP/PSP V PID value. Disconnect jumper wire and record PSP/PSP V PID value. If PSP PID value changed from high to low, replace PSP switch. If PSP/PSP V PID value did not change as specified, go to next step. - 3) Check PSP Circuit For Open
Turn ignition switch to OFF position. Disconnect PCM connector(s). Inspect connector for loose, damaged or corroded terminals. Repair as necessary. Using a DVOM, measure resistance of PSP circuit between PCM harness connector terminal and PSP switch harness connector terminal. See Fig 1 or Fig 2 . Using a DVOM, measure resistance of SIG RTN circuit between PCM harness connector terminal and PSP switch harness connector terminal. If both resistance measurements are less than 5 ohms, go to next step. If either resistance measurement is 5 ohms or more, repair open in PSP or SIG RTN circuit.Courtesy of FORD MOTOR CO.
- 4) Check PSP Circuit For Short SIG RTN Or Ground
Using a DVOM, measure resistance between PSP switch harness connector PSP SIG and SIG RTN terminals. See Fig 1 or Fig 2 . Using a DVOM, measure resistance between chassis ground and PSP switch harness connector PSP SIG terminal. If both resistance measurements are more than 10 k/ohms, replace PCM. If either resistance measurement is 10 k/ohms or less, repair short between affected circuits.NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 4) to step 10). No test procedures have been omitted. - 10) Continuous Memory DTC P1651: Check PSP Circuits For Intermittent
DTC P1651 is set when PCM does not detect a change in PSP signal input during a calibratable number of speed changes. Possible causes for these faults are:- Vehicle Towed With Engine Running
- Power Steering Hydraulic Problem Repaired, But DTC Not Cleared
- Faulty PSP Switch/Shorting Bar Damage
- SIG RTN Circuit Open
- PSP Circuit Open Or Shorted To SIG RTN
- Faulty Powertrain Control Module (PCM)
Ensure scan tool is connected to Data Link Connector (DLC). Turn ignition switch to ON position. Using scan tool, select PSP PID from PID/DATA MONITOR & RECORD menu. While observing PSP/PSP V PID, lightly tap on PSP switch and wiggle sensor connector to simulate road shock. Wiggle and bend circuits between PSP switch and PCM. A fault is indicated by a sudden change of PSP/PSP V PID value. If fault is indicated, turn ignition switch to OFF position, isolate area and repair as necessary. If no fault is indicated, turn ignition switch to OFF position, reconnect PSP switch connector and go to TEST Z, step 1).