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.
2012 Mazda CX-9 AWD V6-3.7LFACTORY OEM SERVICE PROCEDURE
Knock Sensor: Testing and Inspection
KNOCK SENSOR (KS) INSPECTION [MZI-3.7]
NOTE:
- Before performing the following inspection, make sure to follow the procedure as indicated in the troubleshooting flowchart. Description and Operation
Resistance Inspection
1. Disconnect the negative battery cable. Removal and Replacement
2. Disconnect the KS connector. Service and Repair
3. Measure the resistance between the following terminals:
- KS terminals A and B (KS (LH))
- KS terminals C and D (KS (RH))
- If not as specified, replace the KS. Service and Repair
- If the KS is normal, but the PID value is out of specification, perform the "Circuit Open/Short Inspection".
KS resistance
- Approx. 4.87 Mohms
Circuit Open/Short Inspection
1. Disconnect the negative battery cable. Removal and Replacement
2. Disconnect the KS connector. Service and Repair
3. Disconnect the PCM connector.
4. Inspect the following wiring harnesses for open or short. (Continuity inspection)
Open circuit
- If there is no continuity, the circuit is open. Repair or replace the wiring harness.
- KS terminal A and PCM terminal 2AH
- KS terminal B and PCM terminal 2AD
- KS terminal C and PCM terminal 2AJ
- KS terminal D and PCM terminal 2AF
Short circuit
- If there is continuity, the circuit is shorted. Repair or replace the wiring harness.
- KS terminal A and power supply
- KS terminal A and body ground
- KS terminal B and power supply
- KS terminal B and body ground
- KS terminal C and power supply
- KS terminal C and body ground
- KS terminal D and power supply
- KS terminal D and body ground
Factory Service Tools
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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.