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.

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HOMESERVICE MANUALSMAZDA20086 S SPORT, 4D HATCHBACK, STANDARDREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 687 (ON-BOARD DIAGNOSTIC (ENGINE CONTROL SYSTEM L3) (2 OF 5))DTC P0123DIAGNOSTIC PROCEDURE

2008 Mazda 6 s Sport, 4D Hatchback, Standard

Diagnostic Procedure

2008 Mazda 6 s Sport, 4D Hatchback, StandardSECTION Diagnostic Procedure

WARNING: This page is about a different car, the 2007 Mazda 6. However, it is still accessible from the selected car via links, so may be relevant.

DTC P0123 DIAGNOSTIC PROCEDURE

STEP	INSPECTION		ACTION
1	VERIFY FREEZE FRAME DATA HAS BEEN RECORDED Has FREEZE FRAME DATA been recorded?	Yes	Go to the next step.
1		No	Record FREEZE FRAME DATA on repair order, then go to the next step.
2	VERIFY RELATED REPAIR INFORMATION AVAILABILITY Check for related Service Bulletins and/or online repair information availability. Is any related repair information available?	Yes	Perform repair or diagnosis according to the available repair information. If the vehicle is not repaired, go to the next step.
2		No	Go to the next step.
3	INSPECT THROTTLE BODY CONNECTOR Turn the ignition switch off. Verify that the throttle body connector is connected securely. Is connector normal?	Yes	Go to the next step.
3		No	Connect the connector securely, then go to Step 10.
4	INSPECT THROTTLE BODY CONNECTION FOR POOR CONNECTION Disconnect throttle body connector. Inspect for poor connection (such as damaged/pulled-out pins, corrosion). Is there any malfunction?	Yes	Repair or replace suspected terminal, then go to Step 10.
4		No	Go to the next step.
5	INSPECT TP SENSOR Perform TP sensor inspection. (See THROTTLE POSITION (TP) SENSOR INSPECTION ). Is TP sensor normal?	Yes	Go to the next step.
5		No	Replace throttle body, then go to Step 10.
6	INSPECT TP1 SIGNAL CIRCUIT FOR SHORT TO POWER SUPPLY Turn ignition switch to ON (Engine off). Measure voltage between throttle body terminal A (wiring harness-side) and body ground. Is voltage above 4.9 V ?	Yes	Repair or replace short to power supply. Then, go to Step 10.
6		No	Go to the next step.
7	VERIFY TP SENSOR GROUND CIRCUIT FOR OPEN CIRCUIT Inspect continuity between throttle body connector terminal B (wiring harness-side) and PCM connector terminal 2AO Inspect continuity between throttle body connector terminal D (wiring harness-side) and PCM connector terminal 2AP Is there continuity?	Yes	Go to the next step.
7		No	Repair or replace open circuit between TP sensor connector terminal B (wiring harness-side) and PCM connector terminal 2AO (wiring harness-side). Then, go to Step 10.
8	INSPECT PCM CONNECTOR FOR POOR CONNECTION Disconnect PCM connector. Inspect for poor connection (such as damaged/pulled-out pins, corrosion). Is there any malfunction?	Yes	Repair terminal, then go to Step 10.
8		No	Go to Step 10.
9	VERIFY TP SIGNAL CIRCUIT FOR SHORT TO CONSTANT VOLTAGE CIRCUIT Inspect continuity between throttle body terminals A and B (wiring harness-side). Is there continuity?	Yes	Repair or replace suspected harness, then go to the next step.
9		No	Go to the next step.
10	VERIFY TROUBLESHOOTING OF DTC P0123 COMPLETED Make sure to reconnect all disconnected connectors. Turn ignition switch to ON (Engine off). Clear the DTC from the PCM memory using the M-MDS or equivalent. Start engine and warm it up completely. Is same DTC present?	Yes	Replace PCM, then go to the next step. (See PCM REMOVAL/INSTALLATION ).
10		No	Go to the next step.
11	VERIFY AFTER REPAIR PROCEDURE Perform the "After Repair Procedure". (See AFTER REPAIR PROCEDURE ). Is any DTC present?	Yes	Go to the applicable DTC inspection. (See DTC TABLE ).
11		No	Troubleshooting completed.

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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.