Diagnostic procedure

WARNING: This page is about a different car, the 2009 Mazda 6. However, it is still accessible from the selected car via links, so may be relevant.

DTC P2178:00 (L5) DIAGNOSTIC PROCEDURE

STEP	INSPECTION		ACTION
1	VERIFY FREEZE FRAME DATA AND DIAGNOSTIC MONITORING TEST RESULTS HAVE BEEN RECORDED Have FREEZE FRAME DATA and DIAGNOSTIC MONITORING TEST RESULTS (fuel system related) been recorded?	Yes	Go to the next step.
1		No	Record FREEZE FRAME DATA and DIAGNOSTIC MONITORING TEST RESULTS on 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 AND STORED DTC Switch the ignition to off, then to ON (engine off). Verify pending and stored DTCs using the M-MDS. Are any other DTCs present?	Yes	Misfire DTC is present. Go to Step 9. Other DTC is present: Go to the applicable DTC inspection (See DTC TABLE [L5] .)
3		No	Driveability concern is present: Go to Step 9. Driveability concern is not present Go to the next step.
4	IDENTIFY TRIGGER DTC FOR FREEZE FRAME DATA Is the DTC P2178:00 on FREEZE FRAME DATA?	Yes	Go to the next step.
4		No	Go to troubleshooting procedures for DTC on FREEZE FRAME DATA (See DTC TABLE [L5] .)
5	VERIFY CURRENT INPUT SIGNAL STATUS Connect the M-MDS to the DLC-2. Access the following PIDs using the M-MDS. (See PCM INSPECTION [L5] .) APP1 APP2 ECT MAF TPREL VSS Is there any signal that is far out of specification when the ignition switched to ON and the engine runs?	Yes	Repair or replace the malfunctioning parts according to the inspection results, then go to Step 21
5		No	Go to the next step.
6	VERIFY CURRENT INPUT SIGNAL STATUS UNDER FREEZE FRAME DATA CONDITION Connect the M-MDS to the DLC-2 Access the following PIDs using the M-MDS under the FREEZE FRAME DATA conditions (See PCM INSPECTION [L5] .) APP1 APP2 ECT MAF TPREL VSS Is there any signal which causes drastic changes?	Yes	Repair or replace the malfunctioning parts according to the inspection results, then go to Step 21
6		No	Go to the next step.
7	INSPECT A/F SENSOR Inspect the A/F sensor. (See AIR FUEL RATIO (A/F) SENSOR INSPECTION [L5] .) Is there any malfunction?	Yes	Go to the next step.
7		No	Go to Step 9.
8	INSPECT EXHAUST GAS LEAKAGE Visually inspect for the exhaust gas leakage between the exhaust manifold and A/F sensor. Is there any leakage?	Yes	Repair or replace the malfunctioning parts according to the inspection results, then go to Step 21.
8		No	Replace the A/F sensor, then go to Step 21. (See AIR FUEL RATIO (A/F) SENSOR REMOVAL/INSTALLATION [L5] .)
9	VERIFY CURRENT INPUT SIGNAL STATUS OF MAF SENSOR Connect the M-MDS to the DLC-2 Start the engine Access the MAF PID using the M-MDS Verify that the MAF PID changes quickly according to engine speed. Is the PID normal?	Yes	Go to the next step.
9		No	Replace the MAF/IAT sensor, then go to Step 21 (See INTAKE-AIR SYSTEM REMOVAL/INSTALLATION [L5] .)
10	INSPECT PURGE CONTROL SYSTEM OPERATION Perform the Purge Control System Inspection. (See ENGINE CONTROL SYSTEM OPERATION INSPECTION [L5] .) Is there any malfunction?	Yes	Repair or replace the malfunctioning parts according to the inspection results, then go to Step 21
10		No	Go to the next step.
11	INSPECT PCV VALVE OPERATION Inspect the PCV valve (See POSITIVE CRANKCASE VENTILATION (PCV) VALVE INSPECTION [L5] .) Is there any malfunction?	Yes	Replace the PCV valve, then go to Step 21. (See POSITIVE CRANKCASE VENTILATION (PCV) VALVE REMOVAL/INSTALLATION [L5] .)
11		No	Go to the next step.
12	INSPECT EGR VALVE OPERATION Perform the EGR Control System Inspection. (See ENGINE CONTROL SYSTEM OPERATION INSPECTION [L5] .) Does the EGR control system work properly?	Yes	Repair or replace the malfunctioning parts according to the inspection results, then go to Step 21
12		No	Go to the next step.
13	INSPECT VARIABLE TUMBLE CONTROL OPERATION Perform the Variable Tumble Control Operation Inspection. (See ENGINE CONTROL SYSTEM OPERATION INSPECTION [L5] .) Is there any malfunction?	Yes	Repair or replace the malfunctioning parts according to the inspection results, then go to Step 21.
13		No	Go to the next step.
14	INSPECT FUEL LINE PRESSURE Inspect the fuel line pressure. (See FUEL LINE PRESSURE INSPECTION [L5] .) Is there any malfunction?	Yes	Fuel pressure is too high: Replace the fuel pump unit, then go to Step 21. (See FUEL PUMP UNIT REMOVAL/INSTALLATION [L5] .) Fuel pressure is low: Go to the next step.
14		No	Go to Step 17.
15	INSPECT FUEL LINE Visually inspect the fuel line from fuel pump to fuel infector for any leakage. Is there any leakage?	Yes	Repair or replace the malfunctioning parts according to the inspection results, then go to Step 21.
15		No	Go to the next step.
16	INSPECT FUEL FILTER Visually inspect the fuel filter for foreign materials or stain. Is there any malfunction?	Yes	Repair or replace the malfunctioning parts according to the inspection results, then go to Step 21.
16		No	Go to Step 21.
17	INSPECT IGNITION SYSTEM Perform the spark test. (See ENGINE CONTROL SYSTEM OPERATION INSPECTION [L5] .) Is strong blue spark visible at each cylinder?	Yes	Go to Step 19.
17		No	Go to the next step
18	INSPECT IGNITION COIL RELATED WIRING HARNESS Inspect the ignition coil related wiring harness condition (intermittent open or short) for all cylinders. Is there any malfunction?	Yes	Repair or replace the malfunctioning wiring harness, then go to Step 21.
18		No	Repair or replace the malfunctioning parts according to the inspection results, then go to Step 21.
19	INSPECT VARIABLE VALVE TIMING CONTROL SYSTEM OPERATION Perform the Variable Valve Timing Control System Operation Inspection. (See ENGINE CONTROL SYSTEM OPERATION INSPECTION [L5] .) Is there any malfunction?	Yes	Repair or replace the malfunctioning parts according to the inspection results, then go to Step 21.
19		No	Go to the next step
20	INSPECT FUEL INJECTOR OPERATION Inspect the fuel injector operation. (See ENGINE CONTROL SYSTEM OPERATION INSPECTION [L5] .) Is there any malfunction?	Yes	Repair or replace the malfunctioning parts according to the inspection results, then go to the next step.
20		No	Go to the next step.
21	VERIFY DTC TROUBLESHOOTING COMPLETED Make sure to reconnect all disconnected connectors. Clear the DTC from the PCM memory using the M-MDS. Start the engine and warm it up completely. Is the PENDING CODE for this DTC present?	Yes	Replace the PCM, then go to the next step. (See PCM REMOVAL/INSTALLATION [L5] .)
21		No	Go to the next step
22	VERIFY AFTER REPAIR PROCEDURE Perform the "AFTER REPAIR PROCEDURE". (See AFTER REPAIR PROCEDURE [L5] .) Are any DTCs present?	Yes	Go to the applicable DTC inspection. (See DTC TABLE [L5] .)
22		No	DTC troubleshooting completed.