Diagnostic Aids

WARNING: This page is about a different car, the 1995 Mazda MX-6 and 1995 Mazda 626. However, it is still accessible from the selected car via links, so may be relevant.

The PSP switch is a normally open switch that closes as pressure in the power steering system increases.

Perform this test when instructed during QUICK TEST or if directed by other test procedures. This test is intended to diagnose:

Power Steering Pressure (PSP) switch.
Wiring harness circuits (PSP and SIG RTN).
Powertrain Control Module (PCM).

To prevent replacement of good components, be aware the following non-EEC related areas may be at fault:

Idle speed/throttle stop adjustment.
Binding throttle shaft/linkage.
Cruise control linkage.
Power steering hydraulic system.

NOTE: A break in step numbering sequence occurs at this point. Procedure skips to step 10). No test procedures have been omitted.

10) KOEO Code 519: Attempt To Eliminate Code 519 Code 519 indicates PSP switch circuit is closed. Possible causes for this fault are:

Damaged PSP switch.
Open circuit in wiring harness.
Faulty PCM.

Turn ignition off. Disconnect PSP switch. Connect jumper wire between PSP switch terminal to SIG RTN terminal at PSP switch wiring harness connector. Repeat KOEO SELF-TEST. Measure resistance between PSP test pin No. 28 and test pin No. 46 at breakout box. If Code 519 is not present, replace PSP switch. Repeat QUICK TEST. If Code 519 is present, go to next step.

11) Check PSP Circuit For Short Turn ignition off. Disconnect PCM 60-pin connector and inspect for damaged pins, corrosion and loose wires. Repair as necessary. Install Breakout Box (49-UN01-058), leaving PCM disconnected. Measure resistance between PSP test pin No. 28 and test pin No. 46 at breakout box. If reading is 10,000 ohms or less, repair short circuit. Remove breakout box, reconnect all components and recheck symptom. If reading is more than 10,000 ohms, replace PCM. Remove breakout box, reconnect all components and recheck symptom.

NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 11) to step 20). No test procedures have been omitted.

20) KOER Code 521: Verify Operator Interaction Code 521 indicates PSP switch did not change states due to open or closed switch. Possible causes for this fault are:

Damaged PSP switch.
Open or shorted circuit in wiring harness.
Front wheels turned but not centered.
Faulty PCM.

If steering wheel was turned 1/2 turn within 2 seconds after engine ID code and then returned to center, go to next step. If steering wheel was not turned, repeat QUICK TEST.

21) Check PCM Closed Circuit Identifying Capabilities Turn ignition off. Disconnect PSP switch. Connect jumper wire between PSP switch terminal and SIG RTN terminal at PSP switch wiring harness connector. Perform KOEO SELF-TEST. If Code 519 is present, remove jumper wire and go to step 23). If Code 519 is not present, remove jumper wire and go to next step.

22) Check Continuity Of PSP Switch Circuits Turn ignition off. Disconnect PCM 60-pin connector and inspect for damaged pins, corrosion and loose wires. Repair as necessary. Install Breakout Box (49-UN01-058), leaving PCM disconnected. Measure resistance between PSP test pin No. 28 at breakout box and PSP switch terminal at PSP switch wiring harness connector. If reading is less than 5 ohms, replace PCM. Remove breakout box, reconnect all components and recheck symptom. If reading is 5 ohms or more, repair open circuit. Remove breakout box, reconnect all components and repeat QUICK TEST.

23) Check PSP Switch With Engine Running (Load & No Load) Turn ignition off. Install Breakout Box (49-UN01-058), leaving PCM connected. Reconnect PSP switch. Start engine and allow it to idle. Measure resistance between test pin No. 28 and test pin No. 46 at breakout box. Turn steering wheel 1/2 turn and return to center position. If resistance changes from less than 30 ohms to infinity and then returns to 30 ohms or less (when steering wheel is centered), PSP switch system is okay. Testing is complete. If reading does not change as indicated, replace PSP switch. Remove breakout box and repeat QUICK TEST.