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CM2150 Electronic Control System – 019-087   Unswitched Battery Supply Circuit

General Information

 TOC

The ECM receives constant voltage from the batteries through the ECM battery supply positive (+) wire that is connected directly to the positive (+) battery post. There is one in-line 30-amp fuse in the ECM supply wire to protect the ECM. The ECM receives switched battery input through the keyswitch input signal when the vehicle keyswitch is turned on. The ECM battery supply negative (-) wire is connected directly to the negative (-) battery post.

The ECM battery supply positive (+) wire and the ECM battery supply negative (-) wire are in the ECM power harness.

Always check the ECM battery supply fuse when troubleshooting the ECM and power supply circuit.

Check the battery voltage. Refer to Procedure 019-008.

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Resistance Check

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Disconnect the ECM power harness connector from the ECM connector.

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Adjust the multimeter to measure resistance.

Insert a test lead into the ECM battery supply negative (-) pin of the ECM power connector. Attach it to a multimeter probe. Touch the other multimeter probe to the engine block ground and measure the resistance.

The multimeter must show 10 ohms or less.

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If the resistance value is not correct, check the ECM power harness.

Repair or replace the ECM power harness.

When the checks have been completed, connect the ECM power harness connector.

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NOTE: Some OEM applications have the ECM power harness with all 4 pins in the connector populated.

Check the battery return wire in the ECM power harness for proper grounding.

Disconnect the harness from the ECM connector.

Check for damaged pins in the ECM and the harness.

Repair or replace any damaged pins.

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Voltage Check

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Check the battery voltage supply at the ECM battery supply positive (+) pin of the ECM power connector.

Turn the keyswitch to the OFF position.

Disconnect the 4-pin ECM power harness connector from the ECM connector.

Set the multimeter to measure VDC.

Measure the voltage from the ECM battery supply positive (+) to ground.

The voltage must read battery voltage at this pin.

If the voltage is not correct, repair or replace the ECM power harness.

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Last Modified:  18-Aug-2006
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