GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2005 🢒 Epica 🢒 Engine 🢒 Engine Controls - 2.0L (L34 GMDAT) 🢒 DTC 014

Circuit Description

The engine coolant temperature (ECT) sensor uses a thermistor to control the signal voltage to the electronic control module (ECM). The ECM applies a voltage to the ECT sensor. When the engine is cold, the ECT sensor resistance is high. Therefore, the ECM will see a high signal voltage. As the engine warms, the ECT sensor resistance becomes less, and the voltage drops. At normal engine operating temperature, the ECT sensor signal will measure about 1.5-2 volts.

Conditions for Setting the DTC
    • The engine has been running for more than 2 seconds.
    • The engine coolant temperature sensor signal voltage indicates an engine coolant temperature above 146°C (294°F).

Diagnostic Aids
    • If the connections are OK, monitor the coolant temperature while moving related connectors and the wiring harness. If the failure is induced, the display on the scan tool will change. This may help to isolate the location of an intermittent malfunction.
    • The Temperature vs Resistance values scale may be used to test the coolant sensor at various temperatures to evaluate the possibility of a shifted or mis-scaled engine coolant temperature sensor which may result in driveability complaints. Refer to Temperature Versus Resistance .

Step

Action

Values

Yes

No

1

Was the Diagnostic System Check performed?

--

Go to Step 2

Go to Diagnostic System Check - Engine Controls

2
  1. Connect the scan tool to the data link connector (DLC).
  2. Run the engine until it reaches operating temperature.

Does the scan tool display the engine coolant temperature within the value specified?

80-110°C (176-230°F)

Go to Diagnostic Aids

Go to Step 3

3
  1. Turn the ignition to LOCK.
  2. Disconnect the engine coolant temperature (ECT) sensor connector.
  3. Turn the ignition ON.

Does the scan tool display the engine coolant temperature below the value specified?

-30°C (-11°F)

Go to Step 4

Go to Step 6

4
  1. Jumper terminals 1 and 2 of the ECT sensor connector.
  2. Turn the ignition ON.

Does the scan tool display the engine coolant temperature above the value specified?

180°C (356°F)

Go to Step 5

Go to Step 6

5
  1. Replace the engine coolant temperature sensor.
  2. Run the engine until it reaches operating temperature.
  3. Perform the Diagnostic System Check.

Did you complete the repair?

--

System OK

--

6

Measure the voltage at the ECT sensor connector terminal 1.

Is the voltage within the value specified?

4.5-5.5 V

Go to Step 7

Go to Step 9

7
  1. Turn the ignition to LOCK.
  2. Disconnect the engine control module (ECM) connector.
  3. Inspect the ECM pins and connector for bent or damaged terminals. Repair or replace as needed.
  4. Inspect the wire between the ECT sensor connector terminal 2 and the ECM connector terminal B2 for a short to ECM reference voltage.

Is the problem found?

--

Go to Step 12

Go to Step 8

8
  1. Replace the ECM. Refer to Engine Control Module Replacement .
  2. Run the engine until it reaches operating temperature.
  3. Perform the Diagnostic System Check.

Did you complete the repair?

--

System OK

--

9

Inspect the wire for a short to ground between the ECT sensor connector terminal 1 and the ECM connector terminal B3.

Is the problem found?

--

Go to Step 13

Go to Step 10

10
  1. Turn the ignition to LOCK.
  2. Disconnect the ECM connector.
  3. Inspect the ECM pins and connector for bent or damaged terminals or pins.

Is the problem found?

--

Go to Step 11

Go to Step 8

11
  1. Repair the connector terminals and straighten the ECM pins as needed.
  2. If the ECM pins are broken, the ECM must be replaced.

Have the terminals and pins been repaired?

--

Go to Step 6

--

12
  1. Repair the short to voltage in the wire between the ECT sensor connector terminal 2 and the ECM connector terminal B2.
  2. Run the engine until it reaches operating temperature.
  3. Perform the Diagnostic System Check.

Did you complete the repair?

--

System OK

--

13
  1. Repair the short to ground in the wire between the ECT sensor connector terminal 1 and the ECM connector terminal B3.
  2. Run the engine until it reaches operating temperature.
  3. Perform the Diagnostic System Check.

Did you complete the repair?

--

System OK

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