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Home >> Ford >> 1988 >> Bronco II 4WD, Standard, M5OD-R1 >> Repair and Diagnosis >> Engine Performance >> System >> EEC-IV CEC System >> Quick Test >> Test B15 - Power Steering Pressure Switch (PSPS)
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Test B15 - Power Steering Pressure Switch (PSPS)

NOTE: Perform this test when Service Code 52 is displayed during QUICK TESTS or when directed here by other test procedures.
Fig 1: Vehicle Speed Sensor Circuit
G72357

To prevent replacement of good components, be aware that the following non-EEC related areas may be at fault: idle speed/throttle stop adjustment, binding throttle shaft/linkage or cruise control linkage.

  1. Code 52 Elimination  - Turn key off and wait 10 seconds. Disconnect PSPS. Install a jumper wire between PSPS circuit and signal return at harness. Repeat KEY ON/ENGINE OFF (KOEO) SELF-TEST  . If code 52 is not displayed, replace PSPS and repeat QUICK TEST  . If code 52 is still displayed, go to next step.
  2. PSPS Harness Check  - Turn key off and wait 10 seconds. Disconnect PSPS and ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box, leaving ECA disconnected. Set DVOM on 200-ohm scale and measure resistance between Test Pin No. 46 and signal return at PSPS connector. Also measure resistance between PSPS harness connector and Test Pin No. 24 (Test Pin No. 23 on 2.5L CFI). If both readings are less than 5 ohms, replace ECA. Repeat QUICK TEST  . If readings are greater than 5 ohms, repair open in circuit. Repeat QUICK TEST.
  3. Checking Switch Integrity  - Connect tachometer and start engine. Allow engine to idle in Park or Neutral. Disconnect PSPS at switch. If RPM increases, replace PSPS. If RPM does not increase, go to next step.
  4. Checking PSPS Harness  - Turn key off and wait 10 seconds. Disconnect PSPS and ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box, leaving ECA disconnected. Set DVOM on 200K-ohm scale. Measure resistance between Test Pin No. 24 (No. 23 on 2.5L CFI) and Test Pin No. 46 at the breakout box. If resistance is 10K ohms or less, repair short in harness. If reading is greater than 10K ohms, replace ECA. Repeat QUICK TEST  .
  5. Engine Running Self-Test Code 52 Displayed  - If you turned steering wheel 1/2 turn any time AFTER engine ID code, but BEFORE dynamic response code, go to next step. If steering wheel was not turned, ensure front wheels are centered (no load condition). Repeat QUICK TEST  .
  6. Checking ECA Open Circuit Identifying Capabilities  - Turn key off and wait 10 seconds. Disconnect PSPS. Perform KEY ON/ENGINE OFF (KOEO) SELF-TEST  . If code 52 is present, go to step 8). If code 52 is not present, go to next step.
  7. PSPS Harness Check  - Turn key off and wait 10 seconds. Disconnect PSPS and ECA 60-pin connector. Inspect connector for damaged pins, corrosion, or loose wires. Install breakout box and set DVOM on 200K-ohm scale. Measure resistance between Test Pins No. 46 and 24 (No. 23 on 2.5L CFI) at breakout box. If reading is 10K ohms or less, repair short to signal return in PSPS circuit. Repeat QUICK TEST  . If reading is 10K ohms or more, replace ECA. Repeat QUICK TEST.
  8. PSPS Position Comparison  - Turn key off and wait 10 seconds. Install breakout box, leaving ECA connected. With PSPS connected, set DVOM on 200-ohm scale. Turn key on and measure resistance between Test Pins No. 24 (No. 23 on 2.5L CFI) and No. 46. Start engine. If reading remains less than 10 ohms between KOEO and engine running, go to next step. If not, go to step 11).
  9. PSPS Position: Load/No Load  - Install breakout box and connect ECA. Connect PSPS and set DVOM on 200-ohm scale. Start engine and allow it to idle. Measure resistance between Test Pins No. 24 (No. 23 on 2.5L CFI) and No. 46 on breakout box. Turn steering wheel 1/2 turn and return. If reading changes from less than 10 ohms to infinity (indicating PSPS opening) and then returns to 10 ohms or less (when steering wheel is centered), PSPS system is okay. Remove breakout box and return to QUICK TEST  . If reading did not change as indicated, go to next step.
  10. PSPS Closed or Low Hydraulic Pressure  - At this point, there are only 2 possible causes for code 52. They are a PSPS switch that will not open, or low available hydraulic pressure. Turn key off and wait 10 seconds. Substitute original switch with a known good PSPS switch. Perform KEY ON ENGINE RUNNING (KOER) SELF-TEST  and turn steering wheel 1/2 turn during test. If code 52 is still present, check for low hydraulic pressure. If code 52 is not present, replace original PSPS switch. Service other codes if necessary.
  11. PSPS Always Open or High Hydraulic Pressure  - At this point, there are only 2 possible causes for code 52. They are a PSPS switch that is always open, or excessively high hydraulic pressure. Turn key off and wait 10 seconds. Substitute original switch with a known good PSPS switch. Perform KEY ON ENGINE RUNNING (KOER) SELF-TEST  and turn steering wheel 1/2 turn during test. If code 52 is still present, check for high hydraulic pressure. If code 52 is not present, replace original PSPS switch. Service other codes if necessary.
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