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 MANUALSMAZDA1999626 ES, 2.5 D, STANDARDREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 432 (ON-BOARD DIAGNOSTIC (ENGINE CONTROL SYSTEM 13BMSP])DTC P0505DIAGNOSTIC PROCEDURE

1999 Mazda 626 ES, 2.5 D, Standard

Diagnostic procedure

1999 Mazda 626 ES, 2.5 D, StandardSECTION Diagnostic procedure

WARNING: This page is about a different car, the 2005 Mazda RX-8. However, it is still accessible from the selected car via links, so may be relevant.

DTC P0505 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 the FREEZE FRAME DATA on the repair order, then go to the next step.
2	VERIFY RELATED REPAIR INFORMATION AVAILABILITY Verify related Service Bulletins and/or on-line 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	VERIFY RELATED PENDING CODE OR STORED DTC Turn the ignition switch off, then to the ON position (Engine off). Verify the related PENDING CODE or stored DTCs. Are other DTCs present?	Yes	Go to the applicable DTC inspection. (See DTC TABLE .)
3		No	Go to the next step.
4	INSPECT DRIVE-BY-WIRE CONTROL SYSTEM OPERATION Perform the "Drive-by-wire Control System Inspection". (See DRIVE-BY-WIRE CONTROL SYSTEM INSPECTION .) Is there any malfunction?	Yes	Repair or replace the malfunctioning part according to the inspection results. Then go to Step 15.
4		No	Go to the next step.
5	INSPECT A/C MAGNETIC CLUTCH OPERATION NOTE: The following test should be performed for A/C. Go to the next step for vehicles without A/C. Turn the blower motor switch off. Is magnetic clutch still on?	Yes	Go to the "NO.24 A/C IS ALWAYS ON OR A/C COMPRESSOR RUNS CONTINUOUSLY.". (See NO.24 A/C IS ALWAYS ON OR A/C COMPRESSOR RUNS CONTINUOUSLY .)
5		No	Go to the next step.
6	INSPECT GENERATOR CONTROL SYSTEM OPERATION Apply the electrical load at idle. Is the engine speed increased?	Yes	Go to the next step.
6		No	Repair or replace the wiring harness for a possible short to power supply, then go to Step 9.
7	INSPECT AIR CLEANER ELEMENT Remove the air cleaner element with engine running. Is the engine speed increased?	Yes	Clean or replace the air cleaner element, then go to Step 14. (See INTAKE-AIR SYSTEM REMOVAL/INSTALLATION .)
7		No	Go to the next step.
8	INSPECT THROTTLE BODY PASSAGE Remove the throttle body. (See INTAKE-AIR SYSTEM REMOVAL/INSTALLATION .) Is throttle body clogged?	Yes	Clean the throttle body passage or replace the throttle body, then go to Step 14. (See INTAKE-AIR SYSTEM REMOVAL/INSTALLATION .)
8		No	Go to the next step.
9	INSPECT ENGINE COMPRESSION Inspect the engine compression. (See COMPRESSION INSPECTION .) Is there any malfunction?	Yes	Go to the next step.
9		No	Go to Step 14.
10	INSPECT METERING OIL PUMP Inspect the metering oil pump. (See METERING OIL PUMP INSPECTION .) Is there any malfunction?	Yes	Repair or replace the malfunctioning part according to the inspection results. Overhaul or replace the engine. Then go to Step 15.
10		No	Go to the next step.
11	INSPECT ENGINE OIL CONDITION Inspect the engine oil condition. Is the engine oil condition normal?	Yes	Go to the next step.
11		No	Replace the engine oil. Inspect the ECT sensor and related harnesses. (See ENGINE COOLANT TEMPERATURE (ECT) SENSOR INSPECTION .) Overhaul or replace the engine. Then go to Step 15.
12	INSPECT OIL PRESSURE Inspect the oil pressure. (See OIL PRESSURE INSPECTION .) Is there any malfunction?	Yes	Repair or replace the malfunctioning part according to the inspection results. Overhaul or replace the engine. Then go to Step 15.
12		No	Go to the next step.
13	INSPECT OIL PASSAGE Inspect the oil pipe between metering oil pump and metering oil nozzle. Is there any malfunction?	Yes	Inspect and repair for leakage or clogging in the engine oil passage. Overhaul or replace the engine. Then go to Step 15.
13		No	Overhaul or replace the engine. Then go to the next step.
14	INSPECT FUEL LINE PRESSURE Perform the "FUEL LINE PRESSURE INSPECTION". (See FUEL LINE PRESSURE INSPECTION .) Is there any malfunction?	Yes	Replace the fuel pump unit, then go to the next step. (See FUEL PUMP UNIT REMOVAL/INSTALLATION .)
14		No	Go to the next step.
15	VERIFY TROUBLESHOOTING OF DTC P0505 COMPLETED Make sure to reconnect all disconnected connectors. Clear the DTC from the PCM memory using the WDS or equivalent. Perform the KOER self-test. Is the same DTC present?	Yes	Replace the PCM, then go to the next step. (See PCM REMOVAL/INSTALLATION .)
15		No	Go to the next step.
16	VERIFY AFTER REPAIR PROCEDURE Perform the "AFTER REPAIR PROCEDURE". (See AFTER REPAIR PROCEDURE .) Are any DTCs present?	Yes	Go to the applicable DTC inspection. (See DTC TABLE .)
16		No	DTC troubleshooting completed.

RENDER: 1.0x

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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.