Diagnostic procedure

WARNING: This page is about a different car, the 2005 Mazda 6. However, it is still accessible from the selected car via links, so may be relevant.

NO. 6 CRANKS NORMALLY BUT WILL NOT START [AJ] DIAGNOSTIC PROCEDURE

STEP	INSPECTION		ACTION
1	NOTE: The following test should be performed on vehicles with immobilizer system. Go to Step 12 for vehicles without immobilizer system. Connect WDS or equivalent to DLC-2. Do the following conditions appear? Engine is not completely started. DTC B1681 is displayed.	Yes	Both conditions appear: Go to Step 3.
1		No	Either or other condition appear: Go to the next step.
2	Does engine stall after approx. 2 s from when engine is started?	Yes	Go to the next step.
2		No	Immobilizer system is okay.
3	Is coil connector securely connected to coil?	Yes	Go to the next step.
3	Is coil connector securely connected to coil?	No	Connect coil connector securely. Return to Step 2.
4	Does security light illuminate?	Yes	Go to the next step.
4	Does security light illuminate?	No	Inspect instrument cluster and wiring harness.
5	Connect WDS or equivalent to DLC-2 and retrieve DTC. Are the following DTCs displayed? DTC B1602, B1603, B1604, B1621, B1622, B1624	Yes	Go to appropriate DTC test.
5		No	Go to the next step.
6	Is there continuity between PCM GND terminals 6/22/23/25/100 and GND?	Yes	Go to the next step.
6		No	Repair or replace wiring harness.
7	Measure voltage between PCM GND terminals 6/22/23/25/100 and coil terminal C. Is voltage below 1.0 V ?	Yes	Go to the next step.
7		No	Repair or replace wiring harness.
8	Turn ignition switch to ON position. Measure voltage PCM terminal 34 and 60. Is voltage B+?	Yes	Go to the next step.
8		No	Repair or replace wiring harness.
9	Disconnect coil connector. Turn ignition switch to ON position (Engine OFF). Is there battery voltage at coil connector terminal D?	Yes	Inspect for following: Open or short circuit between coil terminal A (harness-side) and PCM terminal 64 (harness-side) Open or short circuit between coil terminal B (harness-side) and PCM terminal 38 (harness-side)
9		No	Repair or replace wiring harness between coil connector terminal D and fuse panel.
10	Verify following: Vacuum connection External fuel shut off or accessory (kill switch, alarm etc.) Fuel quality: proper octane, contamination, winter/summer blend No air leakage from intake-air system Proper sealing of intake manifold and components attached to intake manifold: EGR valve Ignition wiring Electrical connections Fuses Smooth operation of throttle valve Are all items okay?	Yes	Go to the next step.
10		No	Service as necessary. Repeat Step 10.
11	Connect WDS or equivalent to DLC-2. Retrieve any DTCs. Are there any DTCs displayed?	Yes	DTC is displayed: Go to appropriate DTC test. Communication error message is displayed: Inspect for the following: Open circuit between main relay terminal C and PCM terminal 34 or 60 Open main relay GND circuit Main relay is stuck open. Open or poor GND circuit (PCM terminal 6, 22, 23, 25 or 100) Poor connection of vehicle body GND
11		No	No DTC is displayed: Go to the next step.
12	Turn ignition switch to ON position (Engine OFF). Disconnect throttle body connector. Measure voltage at throttle body VREF terminal with ignition switch at ON position. Is voltage 4.5-5.5 V?	Yes	Go to the next step.
12		No	Inspect and repair open or short circuit between PCM terminal 35 and throttle body VREF terminal.
13	Turn ignition switch to OFF position. Disconnect APP sensor connector. Measure voltage at APP sensor VREF terminal with ignition switch at ON position. Is voltage 4.5-5.5 V?	Yes	Go to the next step.
13		No	Repair or replace open or short circuit for the following: PCM terminal 7 and APP sensor terminal D PCM terminal 8 and APP sensor terminal A
14	Will engine start and run smoothly at part throttle?	Yes	Inspect electronic throttle control system operation (See ELECTRONIC THROTTLE CONTROL INSPECTION .)
14	Will engine start and run smoothly at part throttle?	No	Go to the next step.
15	Connect WDS or equivalent to DLC-2. Access RPM PID. Is RPM PID indicating engine speed when cranking engine?	Yes	Go to the next step.
15		No	Inspect for the following: Open or short circuit in CKP sensor Open or short circuit between CKP sensor and PCM terminal 1 or 27 Open or short circuit in CKP sensor harnesses If CKP sensor and harness are okay, go to the next step.
16	Visually inspect CKP sensor and teeth of crankshaft pulley. Are CKP sensor and teeth of crankshaft pulley okay?	Yes	Go to the next step.
16		No	Replace malfunctioning part.
17	Inspect ignition coil related harnesses condition (intermittent open or short) for all cylinders. Are all harnesses condition okay?	Yes	Go to the next step.
17		No	Repair suspected wiring harness.
18	Perform spark test. (See SPARK TEST .) Is strong blue spark visible at each cylinder?	Yes	Go to the next step.
18		No	Repair or replace malfunctioning part according to malfunction results.
19	Inspect spark plug conditions. Is spark plug wet, covered with carbon or grayish white?	Yes	Spark plug is wet or covered with carbon: Inspect for fuel leakage from injector. Spark plug is grayish white: Inspect for clogged fuel injector.
19		No	Install spark plugs on original cylinders. Go to the next step.
20	Remove and shake PCV valve. Does PCV valve rattle?	Yes	Go to the next step.
20	Remove and shake PCV valve. Does PCV valve rattle?	No	Replace PCV valve.
21	Inspect for restriction in the exhaust system. Is there any restriction?	Yes	Inspect exhaust system.
21		No	Go to the next step.
22	Install fuel pressure gauge between pulsation damper and fuel distributor. Short check connector terminal F/P to body GND using a jumper wire. (See AFTER REPAIR PROCEDURE .) Turn ignition switch to ON (Engine OFF). Is fuel line pressure correct when ignition switch is cycled ON/OFF five times? (See FUEL LINE PRESSURE INSPECTION .)	Yes	Go to the next step.
22		No	Zero or low: Inspect fuel pump relay and fuel pump circuit. Inspect for clogged fuel line. If okay, replace fuel pump unit. (See FUEL PUMP UNIT REMOVAL/INSTALLATION .) High: Replace fuel pump unit. (See FUEL PUMP UNIT REMOVAL/INSTALLATION .)
23	Visually inspect for fuel leakage at fuel injector O-ring and fuel line. Service as necessary. Is fuel line pressure held after ignition switch is turned to OFF position?	Yes	Go to the next step.
23		No	Inspect fuel injector. (See FUEL INJECTOR INSPECTION [AJ] .) If fuel injector is okay, replace fuel pump unit. (See FUEL PUMP UNIT REMOVAL/INSTALLATION .)
24	Disconnect vacuum hose between purge solenoid valve and intake manifold from purge solenoid valve side. Plug opening end of vacuum hose. Attempt to start engine. Is starting condition improved?	Yes	Inspect if purge solenoid valve is stuck open mechanically. Inspect EVAP control system.
24		No	Go to the next step.
25	Is air leakage felt or heard at intake-air system components while racing engine to higher speed?	Yes	Repair or replace.
25		No	Go to the next step.
26	Inspect engine condition while tapping EGR valve housing. Does engine condition improve?	Yes	Replace EGR valve. (See EGR VALVE REMOVAL/INSTALLATION [AJ] .)
26		No	Go to the next step.
27	Perform variable valve timing control system operation inspection. (See VARIABLE VALVE TIMING CONTROL SYSTEM OPERATION INSPECTION .) Does variable valve timing control system work properly?	Yes	Go to the next step.
27		No	Repair or replace malfunctioning part according to variable valve timing control system operation inspection results.
28	Is engine compression correct? (See COMPRESSION INSPECTION .)	Yes	Inspect valve timing.
28		No	Inspect for causes.
29	Verify test results. If okay, return to diagnostic index to service any additional symptoms. If malfunction remains, inspect related Service Bulletins and/or On-line Repair Information and perform repair or diagnosis. If vehicle is repaired, troubleshooting completed. If vehicle is not repaired or additional diagnostic information is not available, reprogram PCM if later calibration is available. Retest.