Diagnostic procedure

WARNING: This page is about a different car, the 2005 Mazda MX-5 Miata. However, it is still accessible from the selected car via links, so may be relevant.

DTC P0301, P0302, P0303, P0304 [BP, BP WITH TC] 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	VERIFY RELATED PENDING CODE OR STORED DTCS Turn ignition key to OFF then ON (Engine off). Verify related pending code or stored DTCs. Is other DTCs present?	Yes	Go to appropriate DTC troubleshooting. (See DTC TABLE )
3		No	Go to the next step.
4	VERIFY CURRENT INPUT SIGNAL STATUS (IGNITION KEY TO ON /IDLE) Access ECT, IAT, MAF, RPM, TP and VSS PIDs using the WDS or equivalent. (See USING SST (WDS OR EQUIVALENT) ) Is there any signal that is far out of specification when ignition switch is ON and engine runs at idle?	Yes	Inspect suspected circuit and/or part according to inspection results. Go to Step 13. (See USING SST (WDS OR EQUIVALENT) )
4		No	Go to the next step.
5	VERIFY CURRENT INPUT SIGNAL STATUS UNDER TROUBLE CONDITION Inspect same PIDs with Step 4 while simulating FREEZE FRAME DATA condition. Is there any signal which causes drastic changes?	Yes	Inspect suspected circuit and/or part according to inspection results. Then go to Step 13. (See USING SST (WDS OR EQUIVALENT) )
5		No	Go to the next step.
6	INSPECT SPARK PLUG CONDITION Turn the ignition switch off. Remove spark plug from suspected cylinder. Check spark plug condition: Cracks Excess wear Gap Wet Is any problem found on spark plug?	Yes	If spark plug is wet, fuel flooding is suspected. Go to Step 12. If spark plug has cracks, excess wear or improper gap, replace faulty spark plug. Then go to Step 13.
6		No	Go to the next step.
7	VERIFY HIGH-TENSION LEAD CONDITION Remove high-tension lead. Check for high-tension lead condition and resistance. Cracks Spark shorts to cylinder head through high-tension lead insulator. Is high-tension lead okay?	Yes	Go to the next step.
7		No	Replace high-tension lead, then go to Step 13.
8	INSPECT INTAKE-AIR SYSTEM FOR AIR SUCTION Inspect for air leakage at following: Around connection TEST LIGHT (LED) of dynamic chamber and intake manifold Around connection of intake manifold and cylinder head Is air leakage found?	Yes	Repair or replace suspected part, then go to Step 13.
8		No	Go to the next step.
9	INSPECT FUEL INJECTOR HARNESS Remove intake air system parts. Disconnect fuel injector connector on suspected cylinder. Connect TEST LIGHT (LED) to fuel injector connector terminals. Check dim of light during cranking. Does TEST LIGHT (LED) illuminate?	Yes	Go to the next step.
9		No	Check for fuel injector harnesses. Repair or replace if necessary, then go to Step 13.
10	INSPECT SEALING OF ENGINE COOLANT PASSAGE WARNING: Removing radiator cap when radiator is hot is dangerous. Scalding coolant and steam may shoot out and cause serious injury. When removing radiator cap, wrap thick cloth around and turn it slowly. Remove radiator cap. Implement procedure to bleed air from engine coolant, then idle engine. Are there any small bubbles which makes engine coolant white the filler opening? NOTE: Large bubbles are normal since they remain air coming out from engine coolant passage.	Yes	Air gets in from poor sealing on head gasket or other areas between combustion chamber and engine coolant passage. Repair or replace faulty parts, then go to Step 12.
10		No	Go to the next step.
11	INSPECT ENGINE COMPRESSION Inspect engine compression. (See COMPRESSION INSPECTION ) Is engine compression okay?	Yes	Go to the next step.
11		No	Overhaul the engine, then go to the next step.
12	INSPECT FUEL INJECTOR OPERATION Remove fuel injector from suspected cylinder. Swap injector with injector on other cylinder. Start engine and idle it. Does misfire DTC move to cylinder which suspected injector?	Yes	Replace injector, then go to Step 13.
12		No	Go to the next step.
13	VERIFY TROUBLESHOOTING OF MISFIRE DTC COMPLETED Make sure to reconnect all disconnected connectors. Start engine. Clear the DTC from the PCM memory using the WDS or equivalent. Perform DRIVE MODE 1. (See MODE 1 (PCM ADAPTIVE MEMORY PRODUCTION DRIVE MODE) ) Is PENDING CODE or stored code for this DTC present?	Yes	Replace PCM, then go to the next step.
13		No	Go to the next step.
14	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 )
14		No	Troubleshooting completed.