LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> Ford >> 1988 >> Bronco II 4WD, Standard, M5OD-R1 >> Repair and Diagnosis >> Engine Performance >> System >> EEC-IV CEC System >> Quick Test >> Test B8 - Throttle Position Sensor (TPS)
April 5, 2026: LEMON Manuals is launched! Read the announcement.

Test B8 - Throttle Position Sensor (TPS)

NOTE: Perform this test when Service Code 23, 53, 63, or 73 is displayed during QUICK TEST.
Fig 1: Throttle Position Sensor (TPS) Circuit
G72352

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, or choke/high cam system (if equipped).

  1. Code 23 Displayed  - If KOEO SELF-TEST code 68 or KOER SELF-TEST codes 31, 41, or 58 are displayed, service these codes first. Disregard code 23 at this time. If these codes have been serviced or are not displayed, go to next step.
  2. Check Throttle Plate  - Inspect throttle body and linkage for mechanical binding or sticking. Make sure linkage is set with throttle in closed position. If throttle plate or linkage is binding, check for binding throttle or cruise control linkage, vacuum line or harness interference, etc. Repair problem(s) and repeat QUICK TEST  . If no mechanical problem is found, go to next step.
  3. Code 53: Generate Code 63  - Turn key off and wait 10 seconds. Disconnect TPS from harness at throttle body. Inspect for and repair any damaged wiring. Perform KEY ON/ENGINE OFF (KOEO) SELF-TEST  . Check for code 63. Ignore all other codes at this time. If code 63 is not displayed, go to step 5). If code 63 is displayed, go to next step.
  4. Check VREF to Signal Return  - Turn key off and wait 10 seconds. Set DVOM on 20-volt scale and disconnect TPS from harness. Inspect for and repair any damaged wiring. With KOEO, measure voltage at TPS connector between VREF and signal return. If reading is less than 4 volts or more than 6 volts, go to TEST A3  , step 1). If reading is between 4 and 6 volts, replace TPS and repeat QUICK TEST  .
  5. Checking TP Signal For Shorts  - Turn key off and wait 10 seconds. Disconnect TPS from harness. Set DVOM on 200K-ohm scale. Disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box, leaving ECA disconnected. Measure resistance between Test Pin No. 47 and Test Pins No. 26 and 57. If either reading is less than 10K ohms, repair short in harness and repeat QUICK TEST  . If both readings are 10K ohms or more, replace ECA and repeat QUICK TEST.
  6. Code 63: Generate Code 53  - Turn key off and wait 10 seconds. Disconnect TPS from harness. Install a jumper wire between VREF and TPS signal at connector. Perform KEY ON/ENGINE OFF (KOEO) SELF-TEST  . Check for codes 53 or 23. Ignore all other codes at this time. If no codes are displayed, immediately remove jumper wire, and go to step 9). If either code 53 or 23 are displayed, replace TPS and repeat QUICK TEST  . If neither code 53 or 23 are displayed, go to next step.
  7. Code 63: Check Voltage VREF to Signal Return  - Turn key off and wait 10 seconds. Disconnect TPS from harness. Inspect for and repair any damaged wiring. Set DVOM on 20-volt scale. Turn key on, leaving engine off. Measure voltage between VREF and signal return at TPS connector. If reading is less than 4 volts or more than 6 volts, go to TEST A3  , step 1). If reading is between 4 and 6 volts, go to next step.
  8. Checking TPS Circuit Continuity  - Turn key off and wait 10 seconds. Leave TPS disconnected. Set DVOM on 200-ohm scale and disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box and connect ECA. Measure resistance between TPS signal at connector and Test Pin No. 47. If reading is 5 ohms or more, repair faulty circuit. Remove breakout box, connect ECA and TPS, and then repeat QUICK TEST  . If reading is less than 5 ohms, go to next step.
  9. Checking Resistance of Ground/Signal Return  - Turn key off and wait 10 seconds. Leave TPS disconnected. Disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box and set DVOM on 200K-ohm scale. Measure resistance at connector between TPS signal and ground, and between TPS signal and Test Pin No. 46. If either reading is less than 10K ohms, repair short circuit and repeat QUICK TEST  . If both readings are 10K ohms or more, replace ECA. Remove breakout box, connect TPS, and then repeat QUICK TEST.
    NOTE: Code 73 in step 10) indicates that TPS did not exceed 25% of its rotation during DYNAMIC RESPONSE CHECK. For additional information see DYNAMIC RESPONSE CHECK  under QUICK TEST DIAGNOSTIC AIDS.
  10. Code 73: TPS Movement  - Turn key off. Install breakout box and set DVOM on 20-volt scale. Connect DVOM to Test Pins No. 46 and 47. Perform KEY ON ENGINE RUNNING (KOER) SELF-TEST  . Verify that DVOM reading exceeds 3.5 volts during WOT of DYNAMIC RESPONSE CHECK. If reading exceeds 3.5 volts, replace ECA and repeat QUICK TEST  . If reading does not exceed 3.5 volts, ensure TPS is correctly installed and adjusted. If okay, replace TPS and repeat QUICK TEST.
  11. Code 53: TPS Movement  - Using CONTINUOUS MONITOR (WIGGLE) TEST  , observe VOM or diagnostic tester for indication of fault while slowly opening throttle to WOT. Slowly bring throttle to closed position, lightly tap TPS and wiggle connector. If no fault is indicated, go to step 13). If fault is indicated, go to next step.
  12. TPS Voltage Measurement  - Turn key off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box, leaving ECA connected. Stay in CONTINUOUS MONITOR (WIGGLE) TEST and connect DVOM between Test Pins No. 47 and 46. Set DVOM on 20-volt scale. Turn key on, leaving engine off. Observe DVOM and repeat step 11). If fault occurs at less than 4.25 volts, inspect TPS connectors and terminals. If okay, replace TPS and repeat QUICK TEST  . If fault does not occur at less than 4.25 volts, TPS over-travel may have caused continuous code 53. TPS is good, go to next step to check harness.
  13. Checking Harness  - While in CONTINUOUS MONITOR (WIGGLE) TEST, shake, bend and wiggle small sections of EEC-IV harness from TPS sensor to firewall, and from firewall to ECA. If fault is indicated, isolate fault in wiring and repair as necessary. Repeat QUICK TEST  . If no fault is indicated, go to next step.
  14. Checking Harness Connectors  - Turn key off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect both connectors and terminals for obvious damage. If connectors and terminals are damaged, repair as necessary. Repeat QUICK TEST  . If connectors and terminals are okay, fault cannot be duplicated at this time. Continuous code 53 testing is complete.
  15. Continuous Code 63 Displayed  - Using CONTINUOUS MONITOR (WIGGLE) TEST  , observe VOM or diagnostic tester for indication of fault while slowly opening throttle to WOT. Slowly bring throttle to closed position and lightly tap TPS and wiggle connector. If fault is indicated, disconnect TPS. Inspect connectors and terminals. If connectors and terminals are okay, replace TPS and repeat QUICK TEST  . If no fault is indicated, go to next step.
  16. Harness Test  - While in CONTINUOUS MONITOR (WIGGLE) TEST, shake, bend and wiggle small sections of EEC-IV harness from TPS sensor to firewall, and from firewall to ECA. If fault is indicated, isolate fault in wiring and repair as necessary. Repeat QUICK TEST  . If no fault is indicated, go to next step.
  17. ECA Connector Test  - Turn key off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect both connectors and terminals for obvious damage. If connectors and terminals are damaged, repair as necessary. Repeat QUICK TEST  . If connectors and terminals are okay, fault cannot be duplicated at this time. Continuous code 63 testing is complete.
scientia non olet · About LEMON Manuals