P2181-COOLING SYSTEM PERFORMANCE
For a complete wiring diagram Refer to Section 8W.
- When Monitored:
Ignition on, engine running, and no ECT DTCs present.
- Set Condition:
The coolant temperature should change at a specific rate. If this rate is too slow or too fast this fault will set. Two trip fault. Three good trips to clear MIL. ETC light will illuminate on first trip failure.
| Possible Causes |
| INTERMITTENT DTC |
| LOW COOLANT LEVEL |
| THERMOSTAT |
| (K2) ECT 1 SIGNAL CIRCUIT SHORTED TO VOLTAGE |
| (K2) ECT 1 SIGNAL CIRCUIT SHORTED TO GROUND |
| (K2) ECT 1 SIGNAL CIRCUIT SHORTED TO (K900) SENSOR GROUND 1 CIRCUIT |
| (K2) ECT 1 SIGNAL CIRCUIT OPEN OR HIGH RESISTANCE |
| (K900) SENSOR GROUND 1 CIRCUIT OPEN OR HIGH RESISTANCE |
| ENGINE COOLANT TEMPERATURE SENSOR 1 |
| POWERTRAIN CONTROL MODULE (PCM) |
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE - STANDARD PROCEDURE).
Diagnostic Test
1. DTC IS ACTIVENOTE: Diagnose and repair any Engine Coolant Temperature (ECT) sensor DTCs before proceeding with this test.
NOTE: Inspect the ECT sensor and related PCM connector terminals for corrosion or damage.
NOTE: Extremely cold ambient temperatures may cause this DTC to set.
Turn the ignition on.
With the scan tool, select View DTCs.
Review DTC information.
Is the Good Trip Counter greater than zero?
Yes
- Refer to the *CHECKING FOR AN INTERMITTENT DTC Diagnostic Procedure. (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING)
No
- Go to 2
2. LOW ENGINE COOLANT LEVEL
Ignition on, engine not running.
WARNING: Allow the engine to cool before opening the cooling system. The system may be under pressure. Extreme burns or scalding may result. Failure to follow these instructions can result in personal injury or death.
Inspect the cooling system for proper coolant level and condition.
Were any problems found?
Yes
- Inspect the vehicle for a coolant leak. Repair as necessary in accordance with the Service Information.
- Perform the PCM Verification Test Ver. 1 (Refer to 9 - ENGINE - STANDARD PROCEDURE).
No
- Go To3
3. THERMOSTAT
Ignition on, engine not running.
NOTE: Allow the engine to cool to ambient temperature before proceeding with this test.
Using the appropriate service information, determine the proper opening temperature of the thermostat.
With a scan tool, read the ECT sensor value. If the engine was allowed to cool completely, the value should be approximately equal to the ambient temperature.
Start the engine and allow it to reach operating temperature while monitoring the ECT sensor value. The sensor value change should be a smooth transition from start up to normal operating temperature. Monitor the actual coolant temperature with a thermometer.
NOTE: As the engine warms up to operating temperature, the actual coolant temperature (thermometer reading) and the coolant temperature value on the scan tool should be relatively close. The thermostat should not open until the engine reaches the temperature specified in the Service Information.
Does the thermostat open at the temperature specified in the Service Information?
Yes
- Go to 4
No
- Replace the thermostat in accordance with the Service Information.
- Perform the PCM Verification Test Ver. 1 (Refer to 9 - ENGINE - STANDARD PROCEDURE).
4. (K2) ECT 1 SIGNAL CIRCUIT SHORTED TO VOLTAGE
Turn the ignition off.
Disconnect the Engine Coolant Temperature Sensor 1 connector.
Disconnect the Powertrain Control Module (PCM) connector.
Turn the ignition on.
Measure the voltage of the (K2) ECT 1 Signal circuit in the Engine Coolant Temperature Sensor 1 harness connector.
Is there any voltage present?
Yes
- Repair the (K2) ECT 1 Signal circuit for a short to voltage.
- Perform the PCM Verification Test Ver. 1 (Refer to 9 - ENGINE - STANDARD PROCEDURE).
No
- Go to 5
5. (K2) ECT 1 SIGNAL CIRCUIT SHORTED TO GROUND
Turn the ignition off.
Measure the resistance between ground and the (K2) ECT 1 Signal circuit in the Engine Coolant Temperature Sensor 1 harness connector.
Is the resistance above 100 ohms?
Yes
- Go to 6
No
- Repair the (K2) ECT 1 Signal circuit for a short to ground.
- Perform the PCM Verification Test Ver. 1 (Refer to 9 - ENGINE - STANDARD PROCEDURE).
6. (K2) ECT 1 SIGNAL CIRCUIT SHORTED TO (K900) SENSOR GROUND 1 CIRCUIT
Measure the resistance between the (K2) ECT 1 Signal circuit and the (K900) Sensor Ground 1 circuit in the Engine Coolant Temperature Sensor 1 harness connector.
Is the resistance above 100 ohms?
Yes
- Go to 7
No
- Repair the (K2) ECT 1 Signal circuit for a short to the (K900) Sensor Ground 1 circuit.
- Perform the PCM Verification Test Ver. 1 (Refer to 9 - ENGINE - STANDARD PROCEDURE).
7. (K2) ECT 1 SIGNAL CIRCUIT OPEN OR HIGH RESISTANCE
Measure the resistance of the (K2) ECT 1 Signal circuit between the Engine Coolant Temperature Sensor 1 harness connector and the Powertrain Control Module (PCM) harness connector.
Is the resistance below 5.0 ohms?
Yes
- Go to 8
No
- Repair the (K2) ECT 1 Signal circuit for an open circuit or high resistance.
- Perform the PCM Verification Test Ver. 1 (Refer to 9 - ENGINE - STANDARD PROCEDURE).
8. (K900) SENSOR GROUND 1 CIRCUIT OPEN OR HIGH RESISTANCE
Measure the resistance of the (K900) Sensor Ground 1 circuit between the Engine Coolant Temperature Sensor 1 harness connector and the Powertrain Control Module (PCM) harness connector.
Is the resistance below 5.0 ohms?
Yes
- Go to 9
No
- Repair the (K900) Sensor Ground 1 for an open circuit or high resistance.
- Perform the PCM Verification Test Ver. 1 (Refer to 9 - ENGINE - STANDARD PROCEDURE).
9. ENGINE COOLANT TEMPERATURE SENSOR 1
Turn the ignition off.
Connect the Powertrain Control Module (PCM) connector.
Connect a jumper wire between the (K900) Sensor Ground 1 circuit and the (K2) ECT 1 Signal circuit in the Engine Coolant Temperature Sensor 1 harness connector.
Turn the ignition on.
With the scan tool, read the Engine Coolant Temperature Sensor 1 signal voltage.
Is the voltage below 1.0 volt with the jumper wire in place?
Yes
- Replace the Engine Coolant Temperature Sensor 1 in accordance with the Service Information.
- Perform the PCM Verification Test Ver. 1 (Refer to 9 - ENGINE - STANDARD PROCEDURE).
No
- Go to 10
10. POWERTRAIN CONTROL MODULE (PCM)
Using the wiring diagram/schematic as a guide, inspect the wiring and connectors between the Engine Coolant Temperature Sensor 1 and the Powertrain Control Module (PCM).
Look for any chafed, pierced, pinched, or partially broken wires.
Look for broken, bent, pushed out or corroded terminals.
Monitor the scan tool data relative to this circuit and wiggle test the wiring and connectors.
Look for the data to change or for the DTC to reset during the wiggle test.
Refer to any Technical Service Bulletins that may apply.
Were any problems found?
Yes
- Repair as necessary.
- Perform the PCM Verification Test Ver. 1 (Refer to 9 - ENGINE - STANDARD PROCEDURE).
No
- Replace and program the Powertrain Control Module (PCM) in accordance with the Service Information.
- Perform the PCM Verification Test Ver. 1 (Refer to 9 - ENGINE - STANDARD PROCEDURE).