GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2004 🢒 Epica 🢒 Engine 🢒 Engine Controls - 2.0L (L34 GMDAT) 🢒 DTC 018

Circuit Description

The electronic control module (ECM) uses the knock sensor (KS) to detect engine detonation, allowing the ECM to retard ignition control spark timing based on the knock sensor signal being received. The knock sensor produces an AC signal. The signal amplitude and frequency are dependent upon the amount of knock being experienced.

Conditions for Setting the DTC
    • The engine speed is above 2,400 RPM.
    • Maximum integrated value is above 110 for at least 2 seconds.
    • Minimum integrated value is below 1 for at least 2 seconds.
    • DTC 016 is not set.
    • Noise value is above 55 counts for at least 5 seconds.
    • Noise value is below 0 counts for at least 5 seconds.

Diagnostic Aids
    • Repair any engine mechanical problem before proceeding with diagnostics.
    • Ensure the correct fuel octane rating is used.

Step

Action

Yes

No

1

Perform the Diagnostic System Check.

Is the Diagnostic System Check complete?

Go to Step 2

Go to Diagnostic System Check - Engine Controls

2
  1. Turn the ignition to LOCK.
  2. Disconnect the electrical connector at the engine control module (ECM).
  3. Connect a digital voltmeter (DVM) to monitor AC voltage between terminal C11 of the ECM connector and ground.
  4. Tap on the engine with an extension near the knock sensor while observing the signal on the DVM.

Is any signal indicated on the DVM while tapping on the engine?

Go to Step 3

Go to Step 4

3
  1. Connect the electrical connector at the ECM.
  2. Disconnect the electrical connector at the knock sensor.
  3. Using a test light to battery positive probe terminal 2 on the ECM side of the knock sensor.

Did the test light illuminate?

Go to Step 6

Go to Step 8

4

Inspect the wire from terminal C11 on the ECM to terminal 1 on the ECM side of the knock sensor for an open, a short to ground, or a short to battery.

Does the wire indicate an open, a short to ground, or a short to battery?

Go to Step 5

Go to Step 7

5

Repair the wire from terminal C11 of the ECM to terminal 1 on the ECM side of the knock sensor.

Is the repair complete?

System OK

--

6

Replace the ECM. Refer to Engine Control Module Replacement .

Is the repair complete?

System OK

--

7

Replace the knock sensor. Refer to Knock Sensor Replacement .

Is the repair complete?

System OK

--

8

Repair the wire from terminal 2 of the knock sensor to terminal D15 of the ECM.

Is the repair complete?

System OK

Go to Step 6