Pontiac Fiero 1988 Service Manual page 622

DRIVEABILITY AND EMISSIONS - FUEL INJECTION (PORT) 6E3-A-39
CODE 24
VEHICLE SPEED SENSOR (VSS) CIRCUIT
2.8L "P" SERIES (PORT)
DISREGARD CODE 24 IF SET WHILE DRIVE WHEELS ARE NOT TURNING.
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• ASSUMES SPEEDOMETER IS WORKING OK.
• CRUISE CONTROL " O F F " .
• RAISE DRIVE W H E E L S .
• "NOTICE": DO NOT PERFORM THIS TEST WITHOUT SUPPORTING
THE LOWER CONTROL ARMS SO THA T THE DRIVE AXLES ARE IN A
NORMAL HORIZONTAL POSITION. RUNNING THE VEHICLE IN
GEAR WITH THE WHEELS HANGING DOWN AT FULL TRAVEL MAY
DAMAGE THE DRIVE AXLES.
• WITH ENGINE IDLING IN G E A R , " S C A N " SHOULD DISPLAY MPH
ABOVE 0.
DOES IT?
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NO
IGNITION " O F F " .
DISCONNECT 15 W A Y I.P. CONNECTOR.
IGNITION " O N . "
PROBE ECM SIDE OF 15-WAY LP.
CONNECTOR TERMINAL " H " WITH
VOLTMETER TO GROUND.
SHOULD DISPLAY 10 VOLTS OR MORE.
DOES IT?
YES
CODE 24 IS INTERMITTENT. IF NO
ADDITIONAL CODES WERE STORED,
REFER TO DIAGNOSTIC AIDS ON
FACING PAGE.
YES
IE
CIRCUIT 437 OPEN OR SHORTED TO
GROUND BETWEEN I.P. CONNECTOR
AND VSS BUFFER OR FAULTY BUFFER.
NO
CIRCUIT437 SHORTED TO GROUND,
OPEN BETWEEN ECM AND I.P.
CONNECTOR, OR FAULTY E C M .
11-20-86
CLEAR CODES AND CONFIRM " C L O S E D LOOP " OPERATION AND NO "SERVICE ENGINE S O O N " LIGHT. 7S 3941-6E