Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Checking Relay And Start Relay Control Signal
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.
- For vehicles with automatic transmission:
The gear selector shall be in position P or N.
- For vehicles with manual transmission:
The gear lever shall be in neutral position.
- 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 test probe lights up, replace the relay.
If test probe does not light up:
- Check fuses.
- Check the cable between the ignition's 50-feed #B2 and Central Electronic Module (CEM) #A42 for short-circuiting to ground and open circuit.
Check the cable between Central Electronic Module (CEM) #E9 and the relay socket #1(86) for short-circuit to ground and open circuit.
- Check the cable between relay socket #2(85) and Engine Control Module (ECM) for short-circuit to voltage and open circuit.
- Check the connector for the ignition for contact resistance as well as damage to pins and connections.
Check the connector for the Central Electronic Module (CEM) with regards to contact resistance as well as damage to pins and connections.
Check the connector for Engine Control Module (ECM) for contact resistance as well as damage to pins and connections.
Remedy as necessary.
Other information
- See CONNECTING THE BREAKOUT BOX, CENTRAL ELECTRONIC MODULE (CEM) .
- See CONNECTING THE BREAKOUT BOX, ENGINE CONTROL MODULE (ECM) .
- See SIGNAL DESCRIPTION CENTRAL ELECTRONIC MODULE (CEM) .
- See IGNITION AND CONTROL SYSTEMS - SPECIFICATIONS, ELECTRICAL/ELECTRONIC .
- For connecting test probe, use loose flat pins.
- see CHECKING WIRING AND TERMINALS
Was a fault detected?
- YES
Refer to VERIFICATION
- NO
Refer to OTHER FAULT-TRACING
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.
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