Test G - Engine Coolant Temperature (ECT) Sensor
NOTE:
For purposes of this test, a "warmed up" engine has a coolant temperature of 50-240°F (10-116°C) for the KEY ON/ENGINE OFF (KOEO) SELF-TEST PROCEDURE
and between 180-240°F (82-116°C) for the KEY ON/ENGINE RUNNING (KOER) SELF-TEST PROCEDURE
. The test procedure will be invalid outside these ranges.
- Code 21 Displayed. Start engine and run it at 2000 RPM for 2 minutes. Check that upper radiator hose is hot and pressurized. Repeat QUICK TEST before continuing. If vehicle stalls, DO NOT service code 21 at this time, go directly to DIAGNOSIS BY SYMPTOM TEST . If code 21 is not displayed, service other codes as necessary (if displayed). If code 21 appears, go to next step.
- Turn key off and wait 10 seconds. Disconnect TPS. Set DVOM on 20-volt scale. Turn key on, leaving engine off. Measure voltage at TPS harness connector between VREF and signal return. If voltage is less than 4.0-volts or higher than 6.0-volts, go to TEST C , step 1). If voltage is between 4 and 6 volts, reconnect TPS and go to next step.
- Make sure engine is fully warmed up for this step. Turn key off and wait 10 seconds. Disconnect wiring harness at ECT sensor. Set DVOM on 200,000 ohm scale and measure resistance of ECT sensor. If reading is 1300-7700 ohms at engine coolant temperature of 240-140°F (116-60°C) with engine off and 1550-4550 ohms at 230-180°F (110-82°C) with engine running, replace ECA, connect ECT sensor, then repeat QUICK TEST. If readings are not correct for coolant temperature, replace ECT sensor, connect harness, and repeat QUICK TEST.
- Code 51 Displayed. Turn key off and wait 10 seconds. Disconnect ECT sensor at wiring harness and inspect wiring for damage or corrosion. Connect a jumper wire between ECT signal and signal return terminals in sensor harness connector. Repeat KEY ON/ENGINE OFF (KOEO) SELF-TEST PROCEDURE . If code 61 is displayed, replace ECT sensor and remove jumper wire. Reconnect harness to ECT sensor and repeat QUICK TEST. If code 61 is not displayed, go to next step.
- Turn key off and wait 10 seconds. With harness disconnected at ECT sensor and jumper removed from harness connector, disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box, leaving ECA disconnected. Set DVOM on 200 ohm scale. Measure resistance between ECT signal at ECT connector and test pin 7. Measure resistance between signal return at ECT connector and test pin 46. If both readings are less than 5 ohms, replace ECA. Remove breakout box and connect ECA and ECT sensor. Repeat QUICK TEST. If either reading is 5 ohms or higher, repair open circuits. Remove breakout box, connect ECA and ECT sensor. Repeat QUICK TEST.
- Code 61 Displayed. Turn key off and wait 10 seconds. Disconnect ECT sensor and inspect connector for damage or corrosion. Repair wiring and repeat KEY ON/ENGINE OFF (KOEO) SELF-TEST PROCEDURE . If code 51 is displayed, replace ECT sensor, connect sensor, then repeat QUICK TEST. If code 51 is not displayed, go to next step.
- Turn key off and wait 10 seconds. Set DVOM on 20-volt scale. Disconnect TPS. Turn key on, leaving engine off. Measure voltage between VREF and signal return at TPS connector. If reading is less than 4.0-volts or higher than 6.0-volts, go to TEST C , step 1). If voltage is between 4.0 and 6.0 volts, connect TPS and go to next step.
- Turn key off and wait 10 seconds. Disconnect harness from ECT sensor. Disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box, leaving ECA disconnected. Set DVOM on 200,000 ohm scale. Measure resistance between test pin 7 and test pins 40, 46, and 60. If any reading is less than 10,000 ohms, repair short circuits. Remove breakout box, connect ECA and ECT sensor, then repeat QUICK TEST. If all readings are 10,000 ohms or higher, replace ECA. Remove breakout box, connect ECA and ECT sensor. Repeat QUICK TEST.
- Continuous Code 21 Displayed. Turn key off and wait 10 seconds. Disconnect all SELF-TEST equipment and prepare vehicle for test drive. While driving vehicle, attempt to copy driving style in which complaint was noticed. If problem occurs, try to maintain condition for 1 or more minutes. After road test, repeat KEY ON/ENGINE OFF (KOEO) SELF-TEST PROCEDURE . If code 21 is present in CONTINUOUS SELF-TEST, make sure that thermostat is working properly. If thermostat functions properly, replace ECT sensor and repeat QUICK TEST. If code 21 is not displayed, fault cannot be duplicated at this time. Continuous code 21 testing is complete.
- Continuous Code 51 or 61 is Displayed. Using the CONTINUOUS MONITOR (WIGGLE) TEST PROCEDURE , observe VOM or STAR tester LED while tapping ECT sensor and wiggling ECT connector. If fault is indicated, disconnect and inspect ECT connector and terminals. If connector and terminals are okay, replace ECT sensor and repeat QUICK TEST. If no fault is indicated, go to next step.
- While in CONTINUOUS MONITOR (WIGGLE) TEST PROCEDURE , observe VOM or STAR tester LED for fault as you bend, shake or wiggle EEC-IV harness. Start at sensor connector and work toward firewall. Also test harness from firewall to ECA in same manner. If fault is indicated, isolate fault in wiring and repair as necessary. Repeat QUICK TEST. If fault is not indicated, go to next step.
- 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 and repeat QUICK TEST. If connectors and terminals are okay, fault cannot be duplicated at this time. Continuous code 51 or 61 testing is complete.