Component Tests and General Diagnostics

Checking the voltage / ground terminal

Power supply engine control module (ECM)
The engine control module (ECM) is supplied power via four voltage inputs on the control module.
With the ignition on, power is supplied to all voltage inputs and the engine control module (ECM) is in active mode.
1. Power input 1, terminal #B16 (#C16) is supplied with power via a fuse from the battery. This power input is used to power the memory in the Engine control module (ECM). In the event of an open-circuit, the engine control module (ECM) will be reset and adaptation values and diagnostic trouble codes (DTCs) and other information in the memory will disappear.
2. Power input 2, terminal #B15 (#C15) is supplied with power via a fuse from the start control module (SCU), ignition position II. This power input is used to activate the engine control module (ECM). When power input 2 is powered, the system relay will be activated and power inputs 3 and 4 will be powered. The engine control module (ECM) will not be activated if there is an open-circuit.
3. Power input 3, terminal #B3 (#C3) is supplied with power via a fuse from the system relay. The system relay is activated by the engine control module (ECM). This power input governs the supply of power to the Engine control module (ECM).
4. Power input 4, terminal #B5 (#C5) is supplied with power via a fuse from the system relay. The system relay is activated by the engine control module (ECM). This power input governs the supply of power to the Engine control module (ECM).

Checking the power supply
Check the power supply cable from the battery to the Engine control module (ECM) terminal #B16 (#C16). Check for an open-circuit. Check for loose connections. Check for contact resistance. Check for oxidation. Check the fuse. The voltage must be approximately battery voltage.
Check the power supply cable from the start control module (SCU) to engine control module (ECM) terminal #B15 (#C15). Check for an open-circuit. Check for loose connections. Check for contact resistance. Check for oxidation. Check the fuse. The voltage must be approximately battery voltage.
Check the power supply from the system relay to engine control module (ECM) terminals #B3 (#C3) and #B5 (#C5). Check for an open-circuit. Check for loose connections. Check for contact resistance. Check for oxidation. Check the fuse. The voltage must be approximately battery voltage when the ignition is on.

Ground terminal engine control module (ECM)
Then engine control module (ECM) has three ground inputs. All ground inputs from the control module are connected via three separate ground leads to the same ground terminal in the car body. See the relevant wiring diagram for further information about the ground terminal.
1. Ground input 1, #B2 (#C2) is power ground and is connected to the ground terminal in the body.
2. Ground input terminal 2, #B4 (#C4), is power ground and is connected to the ground terminal in the car body.
3. Ground input terminal 3, #B6 (#C6), is power ground and is connected to the ground terminal in the car body.

Checking the ground terminal
Check the ground lead between engine control module (ECM) ground terminals #B2 (#C2), #B4 (#C4) and #B6 (#C6). Check for an open-circuit. Check for loose connections. Check for contact resistance. Check for oxidation. With the ignition on, the drop in voltage between the ground connection for the control module and the ground terminal must not be greater than 0.5 V.
Remedy as necessary.

Other information
- Connecting the breakout box, B6304T2 Connecting the Breakout Box
- Signal specification, B6304T2 Signal Description, Engine Control Module (ECM)
- See the relevant wiring diagram for information about circuit and ground terminals in the bodywork
- Checking wiring and terminals Checking Wiring and Terminals

Troubleshooting procedure complete.

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