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.
2007 Mazda 3 L4-2.0LFACTORY OEM SERVICE PROCEDURE
Knock Sensor: Testing and Inspection
KNOCK SENSOR (KS) INSPECTION[LF, L3]
NOTE: Before performing the following inspection, make sure to follow the procedure as indicated in the troubleshooting flowchart.
Resistance Inspection
1. Disconnect the knock sensor connector.
2. Measure resistance between KS terminals A and B.
- If not within the specification, replace the KS.
- If the monitor item status/specification (reference) is not within the specification, even though the KS resistance is within the specification, perform the "Circuit Open/Short Inspection".
Resistance : Approx. 4.87 megohms
Circuit Open/Short Inspection
1. Disconnect the PCM connector.
2. Inspect the following wiring harnesses for an open or short circuit. (Continuity inspection)
Open circuit
- If there is no continuity, there is an open circuit. Repair or replace the wiring harness.
- Knock sensor terminal A and PCM terminal2U*1,2Q*2
- Knock sensor terminal B and PCM terminal2V*1,2R*2
Short circuit
- If there is continuity, there is a short circuit. Repair or replace the wiring harness.
- Knock sensor terminal A and power supply
- Knock sensor terminal A and body ground
- Knock sensor terminal B and power supply
- Knock sensor terminal B and body ground
*1 : California emission regulation applicable model and except for California emission regulation applicable model with LF MTX,
*2 :L3 Except for California emission regulation applicable model with LF ATX
NOTE: Before performing the following inspection, make sure to follow the procedure as indicated in the troubleshooting flowchart.
Resistance Inspection
1. Disconnect the knock sensor connector.
2. Measure resistance between KS terminals A and B.
- If not within the specification, replace the KS.
- If the monitor item status/specification (reference) is not within the specification, even though the KS resistance is within the specification, perform the "Circuit Open/Short Inspection".
Resistance : Approx. 4.87 megohms
Circuit Open/Short Inspection
1. Disconnect the PCM connector.
2. Inspect the following wiring harnesses for an open or short circuit. (Continuity inspection)
Open circuit
- If there is no continuity, there is an open circuit. Repair or replace the wiring harness.
- Knock sensor terminal A and PCM terminal2U*1,2Q*2
- Knock sensor terminal B and PCM terminal2V*1,2R*2
Short circuit
- If there is continuity, there is a short circuit. Repair or replace the wiring harness.
- Knock sensor terminal A and power supply
- Knock sensor terminal A and body ground
- Knock sensor terminal B and power supply
- Knock sensor terminal B and body ground
*1 : California emission regulation applicable model and except for California emission regulation applicable model with LF MTX,
*2 :L3 Except for California emission regulation applicable model with LF ATX
Factory Service Tools
Use the Manual With the Right Hardware
Pair factory procedures with proven DIY tools so the instructions are easier to execute.
Disclosure: Verified tool recommendations may earn an affiliate commission at no cost to you.
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.
Rather have a pro handle this?
A certified mobile mechanic comes to your home or office. They bring the tools, you stay comfortable. No tow truck, no waiting room, no surprises.
Comes to youSame-day available12-month warranty
Get a Free QuoteNo obligation. See pricing before you book.