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 ECA may be equipped with PSPS software strategy. If a KOEO Code 52/519 is displayed, check if vehicle is equipped with power steering. If vehicle is not equipped with power steering, disregard Code 52/519. This test is only intended to diagnose:

• Power Steering Pressure Switch (PSPS).
• PSPS and SIG RTN wiring harness circuits.
• ECA.

To prevent replacement of good components, be aware 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.

Fig 1: Power Steering Pressure Switch (PSPS) Circuit

1) Code 52/519: Attempt To Eliminate Code  Code 52/519 indicates PSPS circuit is open. Turn ignition off. Disconnect PSPS switch. Install jumper wire between PSPS terminal and SIG RTN terminal at wiring harness connector. Repeat KOEO SELF-TEST  . If Code 52/519 is not displayed, replace PSPS and repeat QUICK TEST  . If Code 52/519 is displayed, remove jumper wire and go to step 2).

2) Check Continuity Of PSPS Circuits  Turn ignition off, and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Set DVOM on 200-ohm scale. Measure resistance between test pin No. 46 and SIG RTN terminal at PSPS wiring harness connector. Also measure resistance between PSPS test pin at breakout box and PSPS terminal at switch wiring harness connector. If both readings are less than 5 ohms, replace ECA and repeat QUICK TEST  . If readings are 5 ohms or more, repair open circuit and repeat QUICK TEST.

3) Check PSPS Operation  Turn ignition off. Connect tachometer, and start engine. Allow engine to idle in Park or Neutral. Disconnect PSPS switch connector. If RPM increases, replace PSPS switch and recheck system. If RPM does not increase, go to step 4).

4) Check PSPS Circuits For Shorts  Turn ignition off. Disconnect PSPS switch. Disconnect ECA 60-pin connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Set DVOM on 200-k/ohm scale. Measure resistance between PSPS test pin at breakout box and test pin No. 46 at breakout box. If resistance is 10,000 ohms or less, repair short in harness and recheck symptom. If reading is more than 10,000 ohms, replace ECA and recheck symptom.

5) KOER SELF-TEST Code 52/521  Disregard this code if vehicle does not have power steering. Code 52/521 indicates PSPS did not change states due to open or closed switch. If steering wheel was turned 1/2 turn within 2 seconds after engine ID code and front wheels were centered in a no-load condition, go to step 6). If steering wheel was not turned, repeat QUICK TEST  .

6) Check ECA Open Circuit Identifying Capabilities  Turn ignition off. Disconnect PSPS. Perform KOEO SELF-TEST  . If Code 52/519 is present, go to step 8). If Code 52/519 is not present, go to step 7).

7) Check PSPS Circuits For Shorts  Turn ignition off. Disconnect PSPS switch. Disconnect ECA 60-pin connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Set DVOM on 200-k/ohm scale. Measure resistance between PSPS test pin and test pin No. 46 at breakout box. If reading is 10,000 ohms or less, repair short circuit and repeat QUICK TEST  . If reading is more than 10,000 ohms, replace ECA and repeat QUICK TEST.

8) Check PSPS Position Comparison  Turn ignition off. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA connected. With PSPS connected, set DVOM on 200-ohm scale. Turn ignition on. Measure resistance between PSPS test pin and test pin No. 46 at breakout box. Start engine. Measure resistance between PSPS test pin and test pin No. 46 at breakout box. If reading shows less than 10 ohms difference between key on engine off and key on engine running, go to step 9). If reading is not as described, replace PSPS switch and repeat QUICK TEST  .

9) Check PSPS With Engine Running (Load & No Load)  Connect PSPS, and set DVOM on 200-ohm scale. Start engine, and allow it to idle. On Taurus 3.0L SHO, ensure clutch is not depressed. On all models, measure resistance between PSPS test pin 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 10 ohms to infinity and then returns to 10 ohms or less (when steering wheel is centered), PSPS system is okay. Testing is complete. If reading does not change as indicated, replace PSPS switch.

10) Code 519: Attempt To Eliminate Code 519  Disregard this code if vehicle does not have power steering. Code 519 indicates PSPS circuit is closed. Turn ignition off. Disconnect PSPS switch connector. Repeat KOEO SELF-TEST  . Measure resistance between PSPS test pin and test pin No. 46 at breakout box. If Code 519 is not present, replace PSPS switch. If Code 519 is present, go to step 11).

11) Check PSPS Circuit For Short  Turn ignition off. Disconnect ECA 60-pin connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Measure resistance between PSPS test pin and test pin No. 46 at breakout box. If reading is 10,000 ohms or less, repair short circuit and repeat QUICK TEST  . If reading is more than 10,000 ohms, replace ECA and repeat QUICK TEST.

15) Check PSPS Operation  Connect tachometer, and start engine. Allow engine to idle in Park or Neutral. Disconnect PSPS switch connector. If RPM increases, replace PSPS switch and recheck system. If RPM does not increase, go to step 16).

16) Check Continuity Of PSPS Circuits  Turn ignition off, and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Set DVOM on 200-ohm scale. Measure resistance between test pin No. 46 and SIG RTN terminal at PSPS wiring harness connector. Also measure resistance between PSPS test pin at breakout box and PSPS terminal at PSPS wiring harness connector. If both readings are less than 5 ohms, replace ECA and repeat QUICK TEST  . If any reading is 5 ohms or more, repair open circuit and repeat QUICK TEST.

20) KOER SELF-TEST Code 521  Disregard this code if vehicle does not have power steering. Code 521 indicates PSPS did not change states due to open or closed switch. If steering wheel was turned 1/2 turn within 2 seconds after engine ID code and front wheels were centered in a no-load condition, go to step 21). If steering wheel was not turned, repeat QUICK TEST  .

21) Check ECA Closed Circuit Identifying Capabilities  Turn ignition off. Disconnect PSPS switch. Connect jumper wire between PSPS terminal and SIG RTN terminal at PSPS 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, go to step 22).

22) Check Continuity Of PSPS Circuits  Turn ignition off, and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Set DVOM on 200-ohm scale. Measure resistance between PSPS test pin at breakout box and PSPS terminal at PSPS wiring harness connector. Also measure resistance between test pin No. 46 at breakout box and SIG RTN terminal at PSPS wiring harness connector. If both readings are less than 5 ohms, replace ECA and repeat QUICK TEST  . If either reading is 5 ohms or more, repair open circuit and repeat QUICK TEST.

23) Check PSPS Position Comparison  Turn ignition off. Install EEC-IV Breakout Box (T83L-50-EEC-IV), leaving ECA connected. With PSPS connected, set DVOM on 200-ohm scale. Turn ignition on. Measure resistance between PSPS test pin and test pin No. 46 at breakout box. Start engine. If reading shows less than 10 ohms difference between key on engine off and key on engine running, go to step 24). If reading is not as described, replace PSPS switch and repeat QUICK TEST  .

24) Check PSPS With Engine Running (Load & No Load)  Start engine, and allow it to idle. Measure resistance between PSPS test pin 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 10 ohms to infinity and then returns to 30 ohms or less (when steering wheel is centered), PSPS system is okay. Testing is complete. If reading does not change as indicated, replace PSPS switch.