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DTC Troubleshooting

DIAGNOSIS PROCEDURE

Step Action YES NO
1  Was "Engine and Emission Control System Check" performed?  Go to Step 2. Go to ENGINE AND EMISSION CONTROL SYSTEM CHECK .
2  Engine coolant temp. check 
  1. Connect scan tool to DLC with ignition switch turned OFF.
  2. Turn ON ignition switch and check engine coolant temp. displayed on scan tool.
  3. Warm up engine to normal operating temp. and check engine coolant temp. displayed on scan tool.

Does engine coolant temp. vary higher than 1°C (1°F) and rise higher than 75°C (167°F)? 		 Intermittent trouble. Check for intermittent referring to INTERMITTENT AND POOR CONNECTION INSPECTION . Go to Step 3.
3  Check ECT sensor harness voltage 
  1. Disconnect connectors from ECT sensor and ECM with ignition switch turned OFF.
  2. Turn ON ignition switch.
  3. Check voltage between "LT GRN" wire terminal of ECT sensor connector and vehicle body ground.

Is voltage about 0 V? 		 Go to Step 4. "LT GRN" wire shorted to other circuits.
If wire are OK, substitute a known-good ECM and recheck.
4  Check ECT sensor harness resistance 
  1. Measure resistance between "C46-12" terminal of ECM connector and "LT GRN" wire terminal of ECT sensor connector with ignition switch turned OFF.

Is resistance below 5 ohm? 		 Go to Step 5. High resistance wire in "LT GRN" circuit.
5  Check ECT sensor ground circuit 
  1. Connect connectors to ECM.
  2. Check for proper connection of ECT sensor at "ORN" wire terminal.
  3. Measure resistance between "ORN" wire terminal of ECT sensor connector and vehicle body ground.

Is resistance below 10 ohm? 		 Go to Step 7. Go to Step 6.
6  Check ECT sensor ground circuit 
  1. Measure resistance between "C46-16" terminal of ECM connector and vehicle body ground.

Is resistance below 5 ohm? 		 Open or high resistance wire in "ORN" circuit.
Poor "C46-16" connection.		 Open or high resistance wire in "C45-6" and/or "C46-6" circuit. If circuit are OK, substitute a known-good ECM and recheck.
7  Check ECT sensor 
  1. Check ECT sensor according to Engine Coolant Temperature (ECT) Sensor Inspection  .

Is it good condition? 		 Go to Step 8. Replace ECT sensor.
8  Thermostat check 
Is there a symptom due to thermostat remaining open (it takes a long time before vehicle heater becomes effective or before engine is warmed to normal operating temp., etc.)? 		 Check thermostat referring to THERMOSTAT INSPECTION . Faulty ECM. Substitute a known-good ECM and recheck.
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