Mazda MX-6 1998, Workshop Manual

Page: 705 / 1282

TROUBLESHOOTING [LA4A-EL]
Pinpoint test DP
DTC P0500 Insufficient vehicle speedometer sensor (VSS) input
DESCRIPTION
This pinpoint test is intended to diagnose the following components:
• Transaxle wiring harness, vehicle speedometer sensor, power circuit
• PCM
POSSIBLE
CAUSE
• Electrical: Battery, input sensors, Wiring harness
• Transaxle: Linkages
Note
• Diagnostic trouble code (DTC) P0500 — go to step DP1
STEP INSPECTION
ACTION
DP1
DTC P0500: CHECK CONTINUITY OF VEHICLE
SPEEDOMETER SENSOR HARNESS CIRCUIT
DTC P0500 indicates the VSS input signal has
been detected out of Self-Test range.
Note
• Delayed engagement or no vehicle movement
may be caused by a transaxle concern. Harsh
shifts and/or erratic speedometer may be
caused by a failed speedometer or an open or
intermittent ground within the instrument panel
on vehicles with electronic readout.
Possible causes:
• Open in VSS (+)/VSS (-) harness circuit.
• Short to GND or VSS ground circuit in VSS
(+)/VSS (-) harness circuit
• Short to VSS power circuit in VSS (+)/VSS
(-) harness circuit
• Damaged VSS
• Damaged PCM
• Key OFF.
• Disconnect PCM. Inspect for damaged or
pushed out pins, corrosion, loose wires, etc.
Service as necessary.
• Install breakout box, PCM disconnected.
• Disconnect VSS.
• Measure resistance between test pin 58 [VSS
(+)] at the breakout box and VSS (+) circuit at
the VSS vehicle harness connector.
• Measure resistance between test pin 33 [VSS
(-)] at the breakout box and VSS (-) circuit at
the VSS vehicle harness connector.
Is each resistance less than 5.0 ohms?
Yes
Go to next step.
No Service open in harness circuit.
Remove breakout box.
Reconnect all components.
Complete PCM.
Reset to clear DTCs.
Run VSS drive cycle in DP5 to verify repair.
DP2 CHECK VEHICLE SPEEDOMETER SENSOR
HARNESS CIRCUITS FOR SHORTS TO
GROUND, VSS GROUND CIRCUIT AND
POWER
• Key off.
• VSS disconnected.
• Breakout box installed, PCM disconnected.
• Measure resistance between test pin
58
and
test pins 24, 61, 76, 103 (power ground), 33,
91 (VSS ground circuit) and 71 (power ground)
at the breakout box.
• Measure resistance between test pins 33 and
71 (power ground) at the breakout box.
Is each resistance greater than 500 ohms?
Yes
Go to next step.
No Service short circuit.
Remove the breakout box.
Reconnect all components.
Complete PCM.
Reset to clear DTCs.
Run VSS drive cycle in DP5 to verify repair.
0 5 -0 1 A -3 0