## Diesel Engine Management System

#### DTC Troubleshooting (cont'd)

11-125

DTC P1536: Incorrect Main Relay Performance

1. Turn the ignition switch OFF.

1. Wait 5 seconds.

1. Turn the ignition switch ON (II).

Is DTC P1536 indicated?

YES – Go to step 4.

NO – Intermittent failure, system is OK at this time. Check for poor connections or loose wires at the main relay and at the ECM.

1. Turn the ignition switch OFF.

1. Check the main relay and ignition feed fuses (20A and 7.5A)

Are both fuses OK?

YES – Go to step 6.

NO – Replace the fuse.

1. Measure the battery voltage at the battery.

Is the battery voltage greater than 9 V?

YES – Go to step 7.

NO – Charge the battery.

1. Turn the ignition switch ON (II).

1. Check the battery voltage with the scan tool.

1. Start the engine and raise the engine speed to 2,000 rpm (min-1).

Is the battery voltage greater than 12 V?

YES – Go to step 17.

NO – Go to step 10.

1. Turn the ignition switch OFF.

1. Disconnect the ECM connector A.

1. Disconnect the ECM A connector terminals No. 13 and No. 1 with a jumper wire.

JUMPER WIRE

1. Turn the ignition switch ON (II).

1. Measure voltage between the ECM A connector terminals No. 4 and No. 2.

Is there battery voltage?

YES – Go to step 15.

NO – Repair open in the wire between the main relay and the ECM, if a problem is not found, replace the main relay.

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