GM Service Manual Online
For 1990-2009 cars only

Circuit Description

The engine controls ignition relay or ENGINE relay, is controlled by the engine control module (ECM) depending upon input from the ignition switch. Battery positive voltage is supplied to the relay coil and switch. When the ignition switch is turned to the ON position, the ECM will provide ground on the control circuit of the relay using a low side driver. This will allow voltage through the relay switch contacts to the components. The ECM monitors the voltage level on the control circuit of the relay. If the ECM detects a short to voltage on the control circuit of the relay, DTC P1610 sets.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC P1610 Engine Controls Ignition Relay Control Circuit High Voltage

Conditions for Running the DTC

    • The ignition is ON or the engine is operating.
    • The DTC runs continuously when the above condition is met.

Conditions for Setting the DTC

The ECM detects a short to voltage on the control circuit of the relay.

Action Taken When the DTC Sets

    • The malfunction indicator lamp (MIL) will illuminate.
    • The ECM will record operating conditions at the time the diagnostic fails. This information will be stored in the Freeze Frame and Failure Records buffers.

Conditions for Clearing the MIL/DTC

    • The MIL will turn OFF after 4 consecutive ignition cycles in which the diagnostic runs without a fault.
    • Using the scan tool can clear DTCs.
    • Disconnect the ECM battery feed for 10 seconds.

Diagnostic Aids

    • For an intermittent condition, refer to Intermittent Conditions .
    • The following table illustrates the ENGINE relay terminal location in the underhood fuse block:

ENGINE Relay Terminal Identification

Feeback

B+ - Coil

Control

B+ - Switch

Front of Vehicle

Step

Action

Yes

No

Schematic Reference: Engine Controls Schematics

Connector End View Reference: Engine Control Module Connector End Views or Engine Controls Connector End Views

1

Did you perform the Diagnostic System Check - Engine Controls?

Go to Step 2

Go to Diagnostic System Check - Engine Controls

2

  1. Turn ON the ignition, with the engine OFF.
  2. Command the engine controls ignition relay ON with a scan tool.

Do you hear an audible click from the relay?

Go to Step 3

Go to Step 4

3

  1. Observe the Freeze Frame/Failure Records data for this DTC.
  2. Turn OFF the ignition for 30 seconds.
  3. Operate the vehicle within the Conditions for Running the DTC.

Did the DTC fail this ignition?

Go to Step 4

Go to Diagnostic Aids

4

  1. Turn OFF the ignition.
  2. Disconnect the ENGINE relay.
  3. Turn ON the ignition, with the engine OFF.
  4. Probe the control circuit of the ENGINE relay with a test lamp connected to a good ground.

Does the test lamp illuminate?

Go to Step 5

Go to Step 7

5

Test the control circuit of the ENGINE relay for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 9

Go to Step 6

6

Test for shorted terminals and poor connections at the engine control module (ECM). Refer to Testing for Intermittent Conditions and Poor Connections and Repairing Connector Terminals in Wiring Systems.

Did you find and correct the condition?

Go to Step 9

Go to Step 8

7

Replace the ENGINE relay.

Did you complete the replacement?

Go to Step 9

--

8

Replace the ECM. Refer to Engine Control Module Replacement .

Did you complete the replacement?

Go to Step 9

--

9

  1. Clear the DTCs with a scan tool.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC.

Did the DTC fail this ignition?

Go to Step 2

Go to Step 10

10

Are there any DTCs that have not been diagnosed?

Go to Diagnostic Trouble Code (DTC) List

System OK