Checking the Starter Motor Relay
Checking the starter motor relay
Checking the power section of the starter relay
Note! The test assumes that the battery is fault free, and that no relevant diagnostic trouble codes (DTCs) for the symptom are stored.
The signal chain to the starter motor can be checked quickly by short-circuiting the relay connections to the starter motor.
Move the gear selector to position P or N. Parking brake applied.
Warning! The starter motor should operate when there is a short-circuit. Be very careful.
Caution! Use two cables with suitable cable terminal when short-circuiting so that the spark does not damage the relay socket.
Remove the starter motor relay and short-circuit the relay socket #3(30) with #5(87), that is, the relay circuit.
Note! Do not bridge directly in the relay base or the connections in the base may be damaged.
If the starter motor now operates there is no fault in the power section of the circuit.
Other information
- For further information about the fuses and relays, see the Wiring Diagram.
Does the starter motor run when the relay is short-circuited?
Yes - Checking the relay and start relay control signal
No - Checking the wiring
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Checking the relay and start relay control signal
Caution! Avoid touching the pins in the control module and the corresponding connector on the cable harness. There is a risk of static discharge which could damage the control module. Discharge yourself and tools to be used by holding the tool's metal part and touching a body part on the car just before starting to work.
- It is possible to deduce whether the fault is in the wiring or in the relay by connecting a electrician's screwdriver over the relay socket coil.
- Move the gear selector to position P or N. Parking brake applied.
Connect a test probe between relay connection #1(86) and #2(85) on the relay socket. Turn the ignition to start position (ignition position III) and observe the light.
If the electrician's screwdriver lights, replace the relay.
If the test probe is not lit, check the cable between the ignition's 50-feed #7 and relay socket #1 (86). Also check the cable between the relay socket #2 (85) and central electronic module (CEM) #A3.
Check the central electronic module (CEM) connector. Check for contact resistance and oxidation.
Remedy as necessary.
Other information
- For connecting breakout box to Central Electronic Module (CEM): Connecting the breakout box Connecting the Breakout Box, Central Electronic Module (CEM)
- Signal description Central Electronic Module (CEM): Signal specification Signal Specification
- Use individual blade terminals to connect the electricians screwdriver
- For further information about the fuses and relays, see the Wiring Diagram
- Checking wiring and terminals Checking Wiring And Terminals
Were any defects found?
Yes - Verification
No - No Fault Found
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Checking the wiring
- Ignition off
- Move the gear selector to position P or N. Parking brake applied.
Maintain the short-circuit between relay base terminals #3 (30) and #5 (87).
Disconnect the control signal cable at solenoid terminal #2 (50). Connect an electrician's screwdriver between the solenoid and the ground terminal.
In start position (ignition position III) the starter motor relay shall be engaged and the test probe shall be lit.
If the electrician's screwdriver lights up, the supply to the solenoid is fault-free and the fault must be in the starter motor If the electrician's screwdriver does not light, check the fuse for the starter motor and supply.
Other information
- Use individual blade terminals to connect the electricians screwdriver
- For further information about the fuses and relays, see the Wiring Diagram.
Continue - DONE
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Verification
Hint: After carrying out the repair, check that the fault has been remedied.
- Ignition off
- Reinstall the connectors, components etc.
- Move the gear selector to position P or N. Parking brake applied.
Turn the ignition key to start position (key position III). The starter motor must run in starting position.
Does the starter motor work?
Yes - FAULT FOUND
No - Fault-tracing information
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Fault-tracing information
Information
Fault-tracing information
The fault should have been detected and remedied. As this is not the case fault-tracing has failed.
Exit fault-tracing for this diagnostic trouble code (DTC) or make another attempt.
Do you want to exit fault-tracing?
Yes - Exit Fault-Tracing
No - Attempt New Test
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Attempt New Test - Checking the power section of the starter relay
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