LEMON Manuals: Even more car manuals for everyone
Home >> Toyota >> 2001 >> Sienna CE >> Repair and Diagnosis >> External Pages >> Different car >> Section 147 (Cruise Control Systems) >> Diagnostic Tests >> DTC 51: Idle Signal Circuit >> Diagnostic Procedure

Diagnostic Procedure

WARNING: This page is about a different car, the 2002 Toyota Avalon. However, it is still accessible from the selected car via links, so may be relevant.
  1. Turn ignition off. Remove cruise control ECU with 16-pin electrical harness connector attached. Locate engine control module and disconnect engine control module 28-pin electrical harness connector E7. See Figure. Turn ignition on. Using a DVOM, backprobe between ground and cruise control ECU 16-pin electrical harness connector terminal No. 13 (Yellow wire). See Figure.
  2. With throttle valve fully open, battery voltage should exist. With throttle valve fully closed, voltage should be less than 2 volts. If voltage is not as specified, go to next step. If voltage is as specified, no problem is indicated at this time. Fault may be intermittent.
  3. Turn ignition off. Reconnect engine control module 28-pin electrical harness connector E7. Disconnect engine control module 24-pin electrical harness connector E5 and throttle position (TP) sensor Black 3-pin electrical harness connector. Using a DVOM, check for open and short circuit conditions in Light Green wire between engine control module 24-pin electrical harness connector E5 terminal No. 23 and TP sensor Black 3-pin electrical harness connector terminal No. 3. See Figure. Also check Blue/Red wire between engine control module 24-pin electrical harness connector E5 terminal No. 2 and TP sensor Black 3-pin electrical harness connector terminal No. 1. If wires, harnesses and connectors are okay, go to next step. If wires, harnesses and connectors are not okay, repair fault as required. See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article. After repairs, perform confirmation test. See CONFIRMATION TEST .
  4. Check TP sensor circuit. See DTC P0120: THROTTLE POSITION SENSOR CIRCUIT in SELF-DIAGNOSTICS - AVALON article in ENGINE PERFORMANCE. If TP sensor circuit is okay, go to next step. If TP sensor circuit is not okay, repair fault as required. After repairs, perform confirmation test. See CONFIRMATION TEST .
  5. Check TP sensor. See THROTTLE POSITION SENSOR in SYSTEM & COMPONENT TESTING - V6 & V8 article in ENGINE PERFORMANCE. If TP sensor is okay, go to next step. If TP sensor is not okay, replace TP sensor. After repairs, perform confirmation test. See CONFIRMATION TEST .
  6. Turn ignition off. Locate engine control module and disconnect engine control module 28-pin electrical harness connector E7. Also disconnect cruise control ECU 16-pin electrical harness connector. See Figure. Using a DVOM, check for open and short circuit conditions in Gray wire between cruise control ECU 16-pin electrical harness connector terminal No. 14 and engine control module 28-pin electrical harness connector E7 terminal No. 24. See Figure. Also check Yellow wire between cruise control ECU 16-pin electrical harness connector terminal No. 13 and engine control module 28-pin electrical harness connector E7 terminal No. 25. If wires, harnesses and connectors are okay, go to next step. If wires, harnesses and connectors are not okay, repair fault as required. See CRUISE CONTROL in SYSTEM WIRING DIAGRAMS article. After repairs, perform confirmation test. See CONFIRMATION TEST .
  7. Turn ignition off. Disconnect cruise control ECU 16-pin electrical harness connector. Using DVOM, check cruise control ECU ground circuit. See CRUISE CONTROL in SYSTEM WIRING DIAGRAMS article. If ground circuit is faulty, repair and retest system. If ground circuit is okay, substitute original cruise control ECU with a known-good unit and recheck system operation. If system operates properly, original cruise control ECU was defective. If system still does not operate properly, perform cruise control ECU pin voltage check. See PIN VOLTAGE TESTS . Check wiring harness and electrical connectors for an intermittent problem. Repair wiring harnesses or connectors as necessary. See CRUISE CONTROL in SYSTEM WIRING DIAGRAMS article. If voltage values, harnesses and connectors are okay, replace cruise control ECU. See CRUISE CONTROL ELECTRONIC CONTROL UNIT  under REMOVAL & INSTALLATION. After repairs, perform confirmation test. See CONFIRMATION TEST .
scientia non olet · About LEMON Manuals