For 1990-2009 cars

### Diagnostic Instructions

• | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

• | Review Strategy Based Diagnosis for an overview of the diagnostic approach.

• | Diagnostic Procedure Instructions provide an overview of each diagnostic category.

### DTC Descriptors

DTC P1610: Engine Controls Ignition Relay Control Circuit High Voltage
DTC P1611: Engine Controls Ignition Relay Control Circuit Low Voltage

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
Ignition 1 Voltage - Coil | P0562, P1611 | P0562, P1611 | -- | --
B+ Voltage - Switch | P0562, P1611 | P0562, P1611 | -- | --
EC Ignition Relay Control | P0563, P1611 | P0562, P1611 | P0562, P1610 | --
EC Ignition Relay Feedback | P0562, P1611 | P0562, P1611 | -- | --

### Circuit/System Description

The Engine Controls (EC) Ignition Relay or Main 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.

### Conditions for Running the DTC

• | The ignition is ON or the engine is operating.

• | The DTCs run continuously once the above condition is met.

### Conditions for Setting the DTC

#### P1610

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

#### P1611

The ECM detects an open or short to ground on the control circuit of the relay.

### Action Taken When the DTC Sets

DTC P1610 and P1611 are Type C DTCs.

### Conditions for Clearing the DTC

DTC P1610 and P1611 are Type C DTCs.

### Reference Information

#### Schematic Reference

Engine Controls Schematics

#### Connector End View Reference

• | Engine Control Module Connector End Views

• | Engine Controls Connector End Views

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

#### DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

#### Scan Tool Reference

• | Scan Tool Data List

• | Scan Tool Data Definitions

• | Scan Tool Output Controls

#### Special Tools Required

• | J 35616 GM-Approved Terminal Test Kit

• | J 43244 Relay Puller Pliers

### Circuit/System Verification

1. With the ignition ON, command the EC ignition relay ON with a scan tool. You should hear an audible click for about 3-5 seconds.
2. If the vehicle passes the Circuit/System Verification Test, then operate the vehicle within the conditions for running the DTC. You may also operate the vehicle within the conditions that are captured in the Freeze Frame/Failure Records List.

### Circuit/System Testing

1. Ignition OFF, disconnect the EC ignition relay.

Important: The test lamp is used to load the circuit and may not illuminate.

2. Connect a test lamp between the ignition 1 voltage circuit of the EC ignition relay and ground.
3. Ignition ON, load test for battery voltage between the ignition 1 voltage circuit of the EC ignition relay and ground.

⇒ | If less than B+, repair the ignition 1 voltage circuit of the EC ignition relay for a short to ground or an open/high resistance.

Important: The test lamp is used to load the circuit and may not illuminate.

4. Connect a test lamp between the B+ voltage circuit of the EC ignition relay and the negative terminal of the battery.
5. Ignition ON, test for less than 0.1 volt between the B+ voltage circuit of the EC ignition relay and the positive battery terminal.

⇒ | If greater than 0.1 volt, repair the B+ voltage circuit of the EC ignition relay for a short to ground or an open/high resistance.

6. With the ignition OFF, connect a test lamp between the control circuit and the ignition 1 voltage circuit of the EC ignition relay.
7. With the ignition ON, use a scan tool to command the EC ignition relay ON. The test lamp should turn ON for about 3-5 seconds and then turn OFF.

⇒ | If the test lamp remains ON all the time, test for a short to ground on the control circuit. If the circuit/connections test normal, replace the ECM.

⇒ | If the test lamp remains OFF all the time, test for a short to voltage or an open/high resistance on the control circuit. If circuit/connections test normal, replace the ECM.

Important: The ignition 1 voltage circuit is between the EC ignition relay and the ECM. The ignition 1 voltage is a feedback circuit.

8. Connect a 15-amp fused jumper wire between the B+ supply voltage circuit and the ignition 1 voltage circuit of the EC ignition relay.
9. Attempt to start the engine. The engine should start.

⇒ | If the engine does not start, test the ignition 1 voltage circuit between the EC ignition relay and the ECM for a short to ground or for an open/high resistance. If the circuit/connections test normal, replace the ECM.

10. If all circuits/connections test normal, test or replace the EC ignition relay.

### Component Testing

1. Measure for 70-110 ohms of resistance between terminals 85 and 86 of the EC ignition relay.

⇒ | If the resistance is not within the specified range, replace the EC ignition relay.

2. Measure for infinite resistance between the following terminals of the EC ignition relay:

• | 30 and 86

• | 30 and 87

• | 30 and 85

• | 85 and 87

⇒ | If continuity is detected, replace the EC ignition relay.

3. Connect a 20-amp fused jumper wire from the positive terminal of the battery to relay terminal 85. Connect a jumper wire from the negative terminal of the battery to relay terminal 86. Measure for less than 2 ohms between terminals 30 and 87 of the relay.

⇒ | If the resistance measures more than 2 ohms, replace the EC ignition relay.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Relay Replacement

• | Control Module References for ECM replacement, setup, and programming