Main Relay Circuit Diagnosis. Chevrolet Vivant 2005

For 1990-2009 cars only

Makes 🢒 Chevrolet 🢒 2005 🢒 Vivant 🢒 Engine 🢒 Engine Controls - 2.0L (L34 GMDAT) 🢒 Main Relay Circuit Diagnosis

Main Relay Circuit Diagnosis Non European Emissions

Circuit Description

When the ignition is turned ON or to the START position, the main relay is energized. The main relay then supplies voltage to the engine fuse box fuse EF25 and the engine fuse box fuse EF26. The direct ignition system ignition coil, the fuel pump relay, coil side. The fuel injectors are supplied voltage through the engine fuse box fuse EF25.

Diagnostic Aids

•	An intermittent problem may be caused by a poor connection, rubbed through wire insulation, or a broken wire inside the insulation.

•	A faulty main relay will cause a no start condition. There will be no voltage supplied to the direct ignition system ignition coil, the fuel pump relay, coil side, or the fuel injectors. Without voltage supplied to these components, they will not operate.

Step	Action	Yes	No
1	Turn the ignition to LOCK. Disconnect the engine fuse block fuses EF25 and EF26. Turn ON the ignition. With a test light connected to ground, probe the fuse terminals nearest the main relay for fuses EF25 and EF26. Is the test light ON at both terminals?	System OK	Go to Step 2
2	Inspect the test light. Is the test light ON at only one terminal?	Go to Step 9	Go to Step 3
3	Inspect the test light. Is the test light OFF at both terminals?	Go to Step 4	--
4	Turn the ignition to LOCK. Inspect the instrument panel fuse block fuse F3. Is the fuse OK?	Go to Step 5	Go to Step 10
5	Disconnect the main relay. Connect a test light between the main relay connector terminal 85 and ground. Turn ON the ignition. Is the test light ON?	Go to Step 6	Go to Step 11
6	Connect a test light between the main relay connector terminal 86 and battery voltage. Is the test light ON?	Go to Step 7	Go to Step 12
7	Connect a test light between the main relay connector terminal 87 and ground. Is the test light ON?	Go to Step 8	Go to Step 13
8	Inspect for an open in the wiring between the main relay connector terminal 30 and the engine fuse block terminals for fuses EF25 and EF26. Is the condition found?	Go to Step 9	Go to Step 14
9	Repair the open in the wiring between the main relay connector terminal 30 and the engine fuse block terminals for fuses EF25 and/or EF26. Is the repair complete?	System OK	--
10	Replace the instrument panel fuse block fuse F15. Is the repair complete?	System OK	--
11	Repair the open in the wiring between the main relay connector terminal 85 and the ignition switch. Is the repair complete?	System OK	--
12	Repair the open in the wiring between the main relay connector terminal 86 and ground. Is the repair complete?	System OK	--
13	Repair the open in the wiring between the main relay connector terminal 87 and the battery. Is the repair complete?	System OK	--
14	Replace the main relay. Is the repair complete?	System OK	--

Main Relay Circuit Diagnosis European Emissions

Circuit Description

When the ignition is turned ON or to the START position, the ignition relay is energized. The ignition relay then supplies voltage to the engine fuse block fuse EF25 and EF26. The electronic ignition (EI) system ignition coil is supplied voltage through the engine fuse block fuse EF26. The fuel injectors are supplied voltage through the engine fuse block fuse EF25.

Diagnostic Aids

•	An intermittent problem may be caused by a poor connection, rubbed through wire insulation, or a broken wire inside the insulation.

•	A faulty ignition 1 relay will cause a no start condition. There will be no voltage supplied to the EI system ignition coil, or the fuel injectors. Without voltage supplied to these components, they will not operate.

Step

Action

Values

Yes

Turn OFF the ignition.
Disconnect the engine fuse block fuse EF25 and EF26.
Turn ON the ignition.
With a test light connected to the ground, probe the fuse terminals nearest the main relay for fuse EF25 and EF26.

Is the light ON at both terminals?

System OK

Go to Step 2

Is the light ON at only 1 terminal?

Go to Step 3

Go to Step 4

Repair the open in the wiring between the main relay connector terminal 30 and the fuse EF25 or EF26 as needed.

Is the repair complete?

System OK

Turn OFF the ignition.
Remove the main relay.
Turn ON the ignition.
With a test light connected to the ground, probe the main relay terminals 85 and 87.

Is the light ON at both terminals?

Go to Step 8

Go to Step 5

Turn OFF the ignition.
Inspect the instrument fuse block fuse F15 or EF5.

Is the fuse open?

Go to Step 6

Go to Step 7

Repair the short circuit between terminal 86 of the main relay and fuse F15 or terminal 87.
Replace fuse F15 or EF5.

Is the repair complete?

System OK

Repair the open circuit between terminal 85 of the main relay and fuse F15 or terminal 87 of the main relay and fuse EF5.

Is the repair complete?

System OK

Go to Step 8

Turn OFF the ignition.
Measure the resistance between the following terminals:

•	Terminal 86 of the main relay and ground

•	Terminal 30 of the main relay and fuse EF25 or EF26

Is the resistance within the specified value?

0 ohms

Go to Step 10

Go to Step 9

Repair the open circuit.

Is the repair complete?

System OK

Replace the main relay.

Is the repair complete?

System OK