GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2004 🢒 Epica 🢒 Engine 🢒 Engine Controls - 2.0L (L34 GMDAT) 🢒 DTC 042

Circuit Description

The electronic ignition (EI) system ignition coil is supplied with battery voltage when the ignition is ON. The electronic control module (ECM) triggers the circuit for the EI system ignition coil. Voltage is then induced in the secondary portion of the EI system ignition coil. Control of the EI system ignition coil is monitored separately for the 2 electronic spark timing lines.

Conditions for Setting the DTC
    • The ECM receives voltage greater than 12 volts through the electronic spark timing (EST) A line while reference pulses are received by the ECM from the crankshaft position (CKP) sensor.
    • This error occurs over 6 times.

Diagnostic Aids
    • Inspect the ECM harness connectors for backed-out terminals, improperly formed or damaged terminals, a poor terminal-to-wire connection, and a damaged wiring harness.
    • If the connections and the harness are OK, connect a digital voltmeter or an oscilloscope between the affected terminal and ground while moving the related connectors and the wiring harness. If the fault is induced, the voltage reading or the scope pattern will change.

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. Disconnect the EI system ignition coil connector.
  2. Inspect the electronic ignition (EI) system ignition coil connector terminals to ensure that the terminals are correctly installed and none of them are touching.

Is the problem found?

--

Go to Step 9

Go to Step 3

3
  1. Measure the voltage between terminal B and terminal C of the EI system ignition coil connector.
  2. Crank the engine.

Does the voltage fluctuate within the value specified?

0.2-2 V

Go to Step 10

Go to Step 4

4
  1. Turn the ignition to LOCK.
  2. Disconnect the engine control module (ECM) connector.
  3. Inspect for any damaged pins or terminals at the ECM connector terminal C14.

Is the problem found?

--

Go to Step 9

Go to Step 5

5
  1. Turn the ignition ON.
  2. Measure the voltage at the EI system ignition coil connector terminal B.

Is any voltage present?

--

Go to Step 7

Go to Step 6

6

Measure the voltage at the EI system ignition coil connector terminal B while moving the connectors and the wiring harness of the ignition circuit.

Is any voltage present?

--

Go to Step 7

Go to Step 8

7
  1. Turn the ignition to LOCK.
  2. Repair the short to voltage between the EI system ignition coil connector terminal B and the ECM connector terminal C14.
  3. Clear any DTCs from the ECM.
  4. Perform the Diagnostic System Check.

Is the repair complete?

--

System OK

--

8
  1. Turn the ignition to LOCK.
  2. Inspect the wires and harnesses of the ignition circuit for any damage that could cause an intermittent short to voltage.

Is the problem found?

--

Go to Step 9

Go to Step 11

9
  1. Repair any wire or connector terminal as needed.
  2. Clear any DTCs from the ECM.
  3. Perform the Diagnostic System Check.

Is the repair complete?

--

System OK

--

10
  1. Turn the ignition to LOCK.
  2. Replace the electronic ignition system ignition coil assembly. Refer to Ignition Coil Replacement .
  3. Clear any DTCs from the ECM.
  4. Perform the Diagnostic System Check.

Is the repair complete?

--

System OK

--

11
  1. Replace the ECM. Refer to Engine Control Module Replacement .
  2. Perform the Diagnostic System Check.

Is the repair complete?

--

System OK

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