Diagnostic Trouble Code (Dtc) P0502 Vehicle Speed Sensor (Vss) Circuit Low Input - Isuzu 1999 RODEO Workshop Manual

6E1–282 RODEO X22SE 2.2L ENGINE DRIVEABILITY AND EMISSION
DIAGNOSTIC TROUBLE CODE (DTC) P0502 VEHICLE SPEED SENSOR (VSS)
Circuit Description
The vehicle speed sensor has a magnet rotated by the
transmission output shaft. Attached to the sensor is a hall
effect circuit that interacts with the magnetic field created
by the rotating magnet. A 12–volt operating supply for the
speed sensor hall circuit is supplied from the meter fuse.
The VSS pulses to ground the 5–volt signal sent from the
powertrain control module (PCM) on the reference circuit.
The PCM interprets vehicle speed by the number of
pulses to ground per second on the reference circuit.
DTC P0502 is a type B code.
Conditions for Setting the DTC
f Engine is running.
f Engine coolant temperature is above 60°C (140°F).
f System voltage is between 10 and 16 volts.
When the above conditions are met, one of the following
tests will run:
Decel Test
f MAP is less than 35 kPa.
f Throttle Position is less than 0.8%.
f Engine Speed is between 1500 RPM and 3500 RPM.
The Decel Test will fail if vehicle speed is less than 8 km/h
(5mph).
CIRCUIT LOW INPUT
The Decel Test will pass if vehicle speed is greater than 24
km/h (15mph).
Power Test
f MAP is greater than 50 kPa.
f Throttle Position is between 25% and 70%.
f Engine Speed is between 2700 RPM and 4400 RPM.
The Power Test will fail if vehicle speed is less than 8 km/h
(5 mph).
The Power Test will pass if vehicle speed is greater than
8km/h (5mph) without any VSS DTC's present, or if
vehicle speed is greater than 49 km/h (30mph) with VSS
Diagnostic Trouble Codes present.
Action Taken When the DTC Sets
f The PCM will illuminate the malfunction indicator lamp
(MIL) the second time the fault is detected.
f Base shift logic on RPM only.
f The PCM will store conditions which were present
when the Diagnostic Trouble Code was set as Freeze
Frame and in the Failure Records data.
Conditions for Clearing the MIL/DTC
f The PCM will turn the MIL OFF on the third consecutive
trip cycle during which the diagnostic has been run and
the fault condition is no longer present.
f A history Diagnostic Trouble Code P0502 will clear
after 40 consecutive warm–up cycles have occurred
without a fault.
D06RX059