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6-52 ENGINE GENERAL INFORMATION AND DIAGNOSIS (TBI FOR G10)
DTC P0121 THROTTLE POSITION CIRCUIT RANGE/PERFORMANCE
PROBLEM
CIRCUIT DESCRIPTION
DTC DETECTING CONDITION POSSIBLE CAUSE
D After engine warmed up.
D While vehicle running at specified engine speed.
D No change in intake manifold pressure (constant throttle opening)
D Difference between actual throttle opening (detected from TP sensor)
and opening calculated by ECM (PCM) (Obtained on the basis of
engine speed and intake manifold pressure) in larger than specified
value.
: 2 driving cycle detection logic, continuous monitoring
D TP sensor malfunction
D High resistance in the circuit
D ECM (PCM) malfunction
DTC CONFIRMATION PROCEDURE
WARNING:
D When performing a road test, select a place where there is no traffic or possibility of a traffic accident
and be very careful during testing to avoid occurrence of an accident.
D Road test should be carried out with 2 persons, a driver and a tester, on a level road.
1) Turn ignition switch OFF. Clear DTC with ignition switch ON, check vehicle and environmental condition for:
– Altitude (barometric pressure): 2400 m, 8000 ft or less (560 mmHg, 75 kPa or more)
– Ambient temp.: –10_C, 14_F or higher
– Intake air temp.: 70_C, 158_F or lower
– Engine coolant temp.: 70 – 110_C, 158 – 230_F
2) Warm up engine to normal operating temperature.
3) Increase vehicle speed to 30 – 40 mph, 50 – 60 km/h in 3rd gear or “D” range and hold throttle valve at that
opening position for 1 min.
4) Stop vehicle.
5) Check DTC in “DTC” mode and pending DTC in “ON BOARD TEST” or “PENDING DTC” mode.
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