Mazda MX-6 1998, Workshop Manual

Page: 324 / 1282

TROUBLESHOOTING [ENGINE CONTROL KL]
DTC P1501
Vehicle speed sensor input signal out of self-test range
DESCRIPTION
• DTC P1501 indicates that VSS input signal is out of self-test range.
Note
• When PCM detects VSS input signal any time during key on engine running (KOER)
testing, DTC P1501 will be set and testing will abort
[Possible Cause]
• Intermittent VSS input signal from external sources such as Ignition wires or charging circuit
STEP
INSPECTION ACTION
1
CHECK PCM VSS PID FOR INPUT SIGNAL
• Start engine and idle in neutral.
• Access VSS PID and observe for vehicle
speed Input to PCM.
• Increase engine speed, no higher than
2000 rpm, several times while observing
VSS PID.
• Is reading on VSS PID less than 5 km/h
{3 mph}?
Yes Unable to duprlcate or identify fault at this time.
RESET PCM to completely clear DTCs.
xr
After Repair Procedure
COMPLETE OBD II Drive Mode.
RERUN OBD Test.
If DTC P1501 still exists.
Intermittent poor connection or component malfunction
(REPAIR or REPLACE as necessary).
No Go to next step.
2 CHECK VSS HARNESS ROUTING
• Check VSS harness routing
• Verify that harness is not routed
adjacent to high current wires (i.e,
ignition wires or generator wiring.)
• Verify VSS harness is shielded and
grounded, if applicable.
• Check continuity of VSS harness.
• Are any problems evident?
Yes SERVICE as necessary.
RESET PCM to completely clear DTCs.
XT After Repair Procedure
COMPLETE OBD II Drive Mode.
No Unable to duplicate or Identify fault at this time.
Intermittent poor connection or component malfunction
(REPAIR or REPLACE as necessary).
DTC P1506 Idle air control (IAC) system overspeed error
DESCRIPTION
• DTC P1506 indicates self-test has detected an IAC system over speed error
[Possible Cause]
• IAC valve circuit short to ground • Damaged IAC valve component
• IAC valve component stuck open • Damaged throttle body
• Vacuum leak • Damaged PCM
STEP
INSPECTION
ACTION
1
CHECK FOR VACUUM LEAKS
• Key on, engine running.
• With engine at idle, listen for vacuum leaks.
• Inspect entire air inlet system from Mass
A ir Flow (MAF) sensor to intake manifold
for damage or leaks such as:
• Cracked or punctured inlet air tube
• Loose air iniet tube at air cleaner hous­
ing or throttle body
• IAC valve component or gasket seal
• Intake manifold assembly or gasket seal
•
EGR valve gasket seal
• Vacuum supply connectors and hose
• Positive crankcase ventilation (PCV)
valve connectors and hose
•
Are any leaks detected in above areas?
Yes SERVICE as necessary.
RECONNECT all components.
RESET PCM to completely clear DTCs.
c r After Repair Procedure
COMPLETE OBD II Drive Mode.
RERUN OBD Test.
No Go to next step.
2 CHECK EVAP SYSTEM FOR STUCK OPEN
PURGE SOLENOID VALVE
• Key off.
• Disconnect hoses at purge solenoid valve.
• Connect hand vacuum pump to port at
solenoid valve.
• Connect hand vacuum pump to either port
if equipped with solenoid valve.
• Apply -5 3 kPa (-4 0 6 mmHg, -1 6 inHg} of
vacuum to purge solenoid valve.
• Does purge solenoid valve hold vacuum
for 20 seconds?
Yes RECONNECT all components.
Go to next step.
No REPLACE purge solenoid valve.
RECONNECT all components.
RESET PCM to completely clear DTCs.
t r After Repair Procedure
COMPLETE OBD II Drive Mode.
RERUN OBD Test.
01-01B-118