Checking the ECM Power and Grounds

CHECKING THE ECM POWER AND GROUNDS


POSSIBLE CAUSES
- ECM ground circuit(s) open
- Fused B+ circuit open
- Fused ignition switch output circuit open

Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding.

Diagnostic Test

1. ECM GROUND CIRCUIT(S) OPEN
Turn the ignition off.
Disconnect the ECM harness connectors.
Using a 12-volt test light connected to 12-volts, check each of the ECM ground circuits in ECM harness connector.

Q: Did the test light illuminate for each cavity?

YES: Go To 2
NO: Repair the ECM Ground circuit(s) for an open.
Perform the POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). Powertrain Verification Test - Ver 1

2. FUSED IGNITION SWITCH OUTPUT CIRCUIT OPEN
Turn the ignition off.
Disconnect the ECM harness connectors.
Turn the ignition on.
Using a 12-volt test light connected to ground, check the Fused Ignition Switch Output circuit in ECM harness connector.

Q: Is the test light on?

YES: Go To 3
NO: Repair the Fused Ignition Switch Output circuit for an open.
Perform the POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). Powertrain Verification Test - Ver 1

3. FUSED B+ CIRCUIT OPEN
Turn the ignition off.
Disconnect the ECM harness connectors.
Using a 12-volt test light connected to ground, check each Fused B+ circuit in the ECM harness connector.

Q: Does the test light illuminate brightly for each circuit?

YES: Test Complete.
Perform the POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). Powertrain Verification Test - Ver 1
NO: Repair the Fused B+ Output circuit for an open.
Perform the POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). Powertrain Verification Test - Ver 1