P2181-COOLING SYSTEM PERFORMANCE

Special Tools: Click to display a list of tools used in this procedure

For a complete wiring diagram, refer to the Wiring Information.

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
LOW COOLANT LEVEL
THERMOSTAT
(K2) ECT SIGNAL CIRCUIT SHORTED TO VOLTAGE
(K2) ECT SIGNAL CIRCUIT SHORTED TO GROUND
(K2) ECT SIGNAL CIRCUIT SHORTED TO THE (K900) SENSOR GROUND CIRCUIT
(K2) ECT SIGNAL CIRCUIT OPEN OR HIGH RESISTANCE
(K900) SENSOR GROUND CIRCUIT OPEN OR HIGH RESISTANCE
ENGINE COOLANT TEMPERATURE (ECT) SENSOR
POWERTRAIN CONTROL MODULE (PCM)

Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).

1. DTC IS ACTIVE

NOTE: 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.

1.	Turn the ignition on.

2.	With the scan tool, select View DTCs.

3.	Review DTC information.

Is the Good Trip Counter greater than zero?

Yes

Perform the INTERMITTENT CONDITION diagnostic procedure. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).

Go To 2

2. LOW ENGINE COOLANT LEVEL

1.	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 possible serious or fatal injury.

2.	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 POWERTRAIN VERIFICATION TEST. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).

Go To 3

3. THERMOSTAT

1.	Ignition on, engine not running.

NOTE: Allow the engine to cool to ambient temperature before proceeding with this test.

2.	Using the appropriate service information, determine the proper opening temperature of the thermostat.

3.	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.

4.	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

Replace the thermostat in accordance with the Service Information.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).

4. (K2) ECT SIGNAL CIRCUIT SHORTED TO VOLTAGE

1.	Turn the ignition off.

2.	Disconnect the Engine Coolant Temperature Sensor harness connector.

3.	Disconnect the Powertrain Control Module (PCM) C2 harness connector.

4.	Turn the ignition on.

5.	Measure the voltage of the (K2) ECT Signal circuit in the Engine Coolant Temperature Sensor 1 harness connector.

Is there any voltage present?

Yes

Repair the (K2) ECT Signal circuit for a short to voltage.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).

Go To 5

5. (K2) ECT SIGNAL CIRCUIT SHORTED TO GROUND

1.	Turn the ignition off.

2.	Measure the resistance between ground and the (K2) ECT Signal circuit in the Engine Coolant Temperature Sensor harness connector.

Is the resistance above 100 Ohms?

Yes

Go To 6

Repair the (K2) ECT Signal circuit for a short to ground.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).

6. (K2) ECT SIGNAL CIRCUIT SHORTED TO THE (K900) SENSOR GROUND CIRCUIT

1.	Measure the resistance between the (K2) ECT Signal circuit and the (K900) Sensor Ground circuit in the Engine Coolant Temperature Sensor harness connector.

Is the resistance above 100 Ohms?

Yes

Go To 7

Repair the (K2) ECT Signal circuit for a short to the (K900) Sensor Ground circuit.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).

7. (K2) ECT SIGNAL CIRCUIT OPEN OR HIGH RESISTANCE

CAUTION:

Do not probe the PCM harness connectors. Probing the PCM harness connectors will damage the PCM terminals resulting in poor terminal to pin connection. Install the GPEC Diagnostic Adaptor to perform the diagnosis.

1.	Connect the Adapter, GPEC Diagnostic 10436 .

2.	Measure the resistance in the (K2) ECT Signal circuit from the ECT Sensor harness connector to the GPEC Adaptor.

Is the resistance below 5.0 Ohms?

Yes

Go To 8

Repair the (K2) ECT Signal circuit for an open circuit or high resistance.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).

8. (K900) SENSOR GROUND CIRCUIT OPEN OR HIGH RESISTANCE

1.	Measure the resistance of the (K900) Sensor Ground circuit between the Engine Coolant Temperature Sensor harness connector and the GPEC Adaptor.

Is the resistance below 5.0 Ohms?

Yes

Go To 9

Repair the (K900) Sensor Ground for an open circuit or high resistance.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).

9. ENGINE COOLANT TEMPERATURE SENSOR

1.	Turn the ignition off.

2.	Connect the PCM C2 harness connector.

3.	Connect a jumper wire between the (K900) Sensor Ground circuit and the (K2) ECT Signal circuit in the ECT Sensor harness connector.

4.	Turn the ignition on.

5.	With the scan tool, read the Engine Coolant Temperature Sensor Signal voltage.

Is the voltage below 1.0 volt with the jumper wire in place?

Yes

Replace the Engine Coolant Temperature Sensor in accordance with the service information. (Refer to 07 - Cooling/Engine/SENSOR, Coolant Temperature - Removal) .
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).

Go To 10

10. POWERTRAIN CONTROL MODULE (PCM)

1.	Using the wiring diagram/schematic as a guide, inspect the wiring and connectors between the Engine Coolant Temperature Sensor and the Powertrain Control Module (PCM).

2.	Look for any chafed, pierced, pinched, or partially broken wires.

3.	Look for broken, bent, pushed out or corroded terminals.

4.	Monitor the scan tool data relative to this circuit and wiggle test the wiring and connectors.

5.	Look for the data to change or for the DTC to reset during the wiggle test.

6.	Perform any Technical Service Bulletins that may apply.

Were any problems found?

Yes

Repair as necessary.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).

Replace and program the Powertrain Control Module (PCM) in accordance with the Service Information. (Refer to 08 - Electrical/8E - Electronic Control Modules/MODULE, Powertrain Control - Removal) .
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).

P2181-COOLING SYSTEM PERFORMANCE

POSSIBLE CAUSES