GM Service Manual Online
For 1990-2009 cars only

Object Number: 52261  Size: SF
Handling ESD Sensitive Parts Notice
Handling ESD Sensitive Parts Notice
Engine Controls Components
Fuel Mixture Input Controls
OBD II Symbol Description Notice

Circuit Description

While the engine is warming, the VCM monitors the ECT sensor in order to determine how long the engine takes to reach the coolant temperature that is required for closed loop operation.

A DTC sets if the VCM determines that the engine did not reach a closed loop temperature in a specified amount of time. This diagnostic will not run if either the intake air or the engine coolant temperature measure below a predetermined temperature. The VCM will only run this DTC on a cold start and only once per cold start. This DTC is a type B DTC.

Conditions for Setting the DTC

    â€¢ The engine is running.
    â€¢ No ECT sensor test failing or DTCs.
    â€¢ No IAT sensor DTCs.
    â€¢ The vehicle speed greater than 1 mph.
    â€¢ The IAT is greater than -9°C.
    â€¢ The ECT is greater than -9°C.
    â€¢ Start-up ECT is at least 40°C.

Action Taken When the DTC Sets

The VCM turns the MIL ON after 2 consecutive driving cycles with the fault active.

Conditions for Clearing the MIL/DTC

The VCM turns OFF the MIL after 3 consecutive driving trips without a fault condition present. A history DTC will clear if no fault conditions have been detected for 40 warm-up cycles (the coolant temperature has risen 22°C (40°F) from the start-up coolant temperature and the engine coolant temperature exceeds 71°C (160°F) during that same ignition cycle) or the scan tool clearing feature has been used.

Diagnostic Aids

When a DTC P0125 sets, a skewed ECT sensor or the engine thermostat that does not operate correctly is indicated.

A poor connection, a rubbed through wire insulation, or a wire broken inside of the insulation may cause an intermittent.

Check for the following conditions:

    â€¢ A poor connection or a damaged harness. Inspect the VCM harness connector for the following conditions:
       - Backed out terminals
       - Improper mating
       - Broken locks
       - Improperly formed or damaged terminals
       - Poor terminal to wire connection and
       - A damaged harness
    â€¢ The intermittent test: If the connections and the harness check OK, monitor a digital voltmeter connected between the VCM terminals while moving the related connectors and the wiring harness. If the failure is induced, the voltage reading changes. This may help in order to isolate the location of the malfunction.

Test Description

The numbers below refer to the step numbers in the diagnostic table.

  1. This test checks the engine warm-up rate.

  2. This test checks the coolant sensor reading on the scan tool and the actual coolant temperature.

Step

Action

Value(s)

Yes

No

1

Important: Before clearing the DTCs, use the scan tool in order to record the Freeze Frame and the Failure Records data. Using the Clear Info function will lose this data.

Was the Powertrain On-Board Diagnostic (OBD) System Check performed?

--

Go to Step 2

Go to Powertrain On Board Diagnostic (OBD) System Check

2

  1. Allow the engine to cool completely.
  2. Install the scan tool.
  3. Turn ON the ignition.
  4. Compare the IAT to the ECT. The values should be close.

Are they close?

--

Go to Step 3

Go to DTC P0117 Engine Coolant Temperature (ECT) Sensor Circuit Low Voltage

3

Check the cooling system coolant level.

Was a problem found?

--

Go to Engine Cooling System

Go to Step 4

4

  1. Start the engine.
  2. Run the engine while the monitoring the ECT on the scan tool.

Does the ECT value rise steadily to above the specified value within 9 minutes?

35°C (95°F)

Go to Diagnostic Aids

Go to Step 5

5

Compare the ECT display on the scan tool to the actual coolant temperature. The values should be close.

Are they close?

--

Go to Engine Cooling System

Go to Step 6

6

Replace the ECT sensor. Refer to Engine Coolant Temperature (ECT) Sensor Replacement .

Is the replacement complete?

--

Go to Step 7

--

7

  1. Using the scan tool, select the DTC and the Clear Info.
  2. Start the Engine.
  3. Idle at the normal operating temperature.
  4. Select the DTC and the Specific.
  5. Enter the DTC number which was set.
  6. Operate the vehicle within the conditions for setting this DTC as specified in the supporting text.

Does the scan tool indicate that this diagnostic ran and passed?

--

Go to Step 8

Go to Step 2

8

Using the scan tool, select the Capture Info and the Review Info.

Are any DTCs displayed that have not been diagnosed?

--

Go to The Applicable DTC Table

System OK