Mazda MX-6 1998, Workshop Manual, Page: 161 / 1282

TROUBLESHOOTING [ENGINE CONTROL FS]
STEP
INSPECTION ACTION
17 Connect NGS tester to DLC.
Access RPM PID.
Is RPM PID indicating engine speed during
cranking of engine?
Yes Go to next step.
No Check following:
• Open or short circuit in CKP sensor.
• Open or short circuit between CKP sensor and PCM.
• Open or short circuit between CKP sensor and
harness.
If CKP sensor and harness okay, go to next step.
18 Visually inspect crankshaft position (CKP)
sensor and teeth of crankshaft pulley.
Is CKP sensor and teeth of crankshaft pulley
okay?
Yes Go to next step.
No
Replace malfunctioning part.
19
Measure gap between crankshaft position
(CKP) sensor and teeth of crankshaft pulley.
Specification
0.5— 1.5 mm {0.02— 0.05 in}
is gap within specifications?
Yes Go to next step.
No Adjust CKP sensor.
2 0
Check for cracks on high tension leads.
Is there any crack on high tension leads? Yes Repair suspected high tension lead.
No Go to next step.
2 1
Is strong blue spark visible at each
disconnected high-tension lead while cranking
engine? Yes
Go to next step.
If symptom occurs with A/C on, go to step 27.
No Check following:
• Open or short circuit in ignition coil.
• Hightension lead(s).
• Open or short circuit in wire harness for ignition system.
• Malfunction of external condenser for eliminating
ignition noise.
• Open circuit between ignition switch and ignition coil.
• Open circuit between ignition coil and PCM.
2 2
Check spark plug conditions.
Is spark plug wet, converted with carbon or
grayish white?
Yes If spark plug is wet or converted with carbon, check for
fuel leak from injector.
If spark plug is grayish white, check clogged for fuel
injector.
No Install spark plugs on original cylinders.
Go to next step.
23
Remove PCV valve and shake PCV valve.
Does PCV valve rattle? Yes Go to next step.
No Replace PCV valve.
24 Is there restriction in the exhaust system?
Is there any restriction? Yes
Check exhaust system.
No Go to next step.
25
Install fuel gauge between fuel filter and fuel
distribution pipe. Connect NGS tester to DLC.
In OUTPUT TEST MODE, select “ALL ON’’
and press start.
Is fuel line pressure correct with ignition switch
ON?
Fuel line pressure
260— 310 kPa
{2.6— 3.2 kgf/cm2, 37— 46 psi>
Yes Go to next step.
No Zero or low:
Check fuel pump circuit.
Check for open fuel pump relief valve.
Check for fuel leak inside pressure regulator.
Check for clogged main fuel line.
High:
Check pressure regulator for high pressure cause.
Check for clogged fuel return line.
26
Visually check for fuel leakage at fuel injector
O-ring, pressure regulator, and fuel line.
Service as necessary. Does fuel line pressure
hold after ignition switch is turned OFF?
Fuel line pressure
More than 150 kPa
{1.5 kgf/cm2, 21 psi> for 5 minutes
Yes Go to next step.
No
Check pressure regulator diaphragm condition.
If condition is okay, check fuel injector.
If condition is not okay, replace pressure regulator.
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