Mazda 626 Station Wagon, Workshop Manual

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TROUBLESHOOTING
Vehicle speed sensor (VSS)
PCM
1. Measure the #1 PCM terminal voltage and confirm
that it is at OV or 5V when the ignition switch is on
and the engine is at idle.
• If it is at OV or 5V, proceed to symptom
troubleshooting No.26 “Intermittent Concerns”.
• If not, inspect the following points concerning
the PCM connector. If there is no problems,
proceed to next step.
— Female terminal opening looseness
— Coupler (pin holder) damage
— Pin discoloration (blackness)
— Harness/pin crimp is loose or
disconnected.
2. Measure the #2 sensor terminal voltage and
confirm that it is at OV or 5V when the ignition
switch is on and the engine at idle.
• If it is at OV or 5V, proceed to symptom
troubleshooting No.26 “Intermittent Concerns”.
• If not, inspect the following points concerning
the sensor connector. If there are no
problems, proceed to next step.
— Female terminal opening looseness
— Coupler (pin holder) damage
— Pin discoloration (blackness)
— Harness/pin crimp is loose or
disconnected.
3. Confirm that the #3 terminal switch voltage is at
OV.
• If it is at OV, inspect the sensor. If necessary,
replace the sensor.
• If not, inspect for the following.
— Open circuit in harness
— Female terminal opening looseness
— Coupler (pin holder) damage
— Pin discoloration (blackness)
— Harness/pin crimp is loose or
disconnected.
ENGINE SYSTEM INSPECTION
Idle Air Control (IAC) Inspection
Engine coolant temperature (ECT) compensation
inspection
1. Connect the SSTs (NGS tester) to DLC.
PROGRAM CARD
2.
Select the PID/DATA MONITOR AND RECORD
function on the NGS display.
3. Select the following PIDs.
• ECT
• IACV
• RPM
4. Verify that the engine is in cold condition, then
start the engine.
5. Verify that the engine speed decreases as the
engine warms up.
• If the engine speed does not decrease or
decreases slowly, carry out the following.
— ECT sensor inspection
— IAC valve inspection
Load compensation inspection
1. Start the engine and run at idle.
2.
Disconnect the IAC valve connector and verify that
the engine speed changes.
• If the engine speed does not change, do as
follows. For GF4A-EL models, go to (6).
(1) Connect the IAC valve connector.
(2)
Connect the SSTs (NGS tester) to DLC.
PROGRAM CARD
(3) Verify that DTC P1504 is not displayed. If
DTC P1504 is shown, carry out DTC
inspection.
(4) Select the SIMULATION TEST function on
the NGS display.
(5) Change the duty value of the IAC valve to
100% using the IACV PID.
(6) Verify that the engine speed increases.
• If the engine speed increases, replace
the PCM.
• If the engine speed does not change,
inspect the following.
F1-149