Diagnostic Trouble Code (Dtc) P0121 Throttle Position (Tp) Sensor Circuit Range/Performance Problem - Isuzu 1999 RODEO Workshop Manual

6E1–132 RODEO X22SE 2.2L ENGINE DRIVEABILITY AND EMISSION
DIAGNOSTIC TROUBLE CODE (DTC) P0121 THROTTLE POSITION (TP) SEN-
SOR CIRCUIT RANGE/PERFORMANCE PROBLEM
Circuit Description
The throttle position (Throttle Position) sensor circuit
provides a voltage signal that changes relative to throttle
blade angle. The signal voltage will vary from about 0.25
volts at closed throttle to about 4.75 volts at wide open
throttle (WOT).
The Throttle Position (TP) signal is used by the
powertrain control module (PCM) for fuel control and
most of the PCM–controlled outputs. The PCM monitors
throttle position and compares actual throttle positions
from the TP sensor to a predicted TP value calculated
from engine speed. If the PCM detects an out–of–range
condition, then a DTC code P0121 will set. DTC P0121 is
type A code.
Conditions for Setting the DTC
f The Engine is running.
f No MAP, ECT, TP, CKP, EGR, EVAP or DTC's are set.
f IAC is between 10 and 160 counts.
f ECT is above –10°C (14°F).
f The MAP value changes by less than 2 kPa.
All the above mentioned conditions are met, and one of
the following conditions occurs for a total of 12.5 seconds
over a 25–second period of time.
Stuck High–
f MAP value is below 55 kPa.
f Actual TP value is greater than the PCM's estimated
TP value (Estimated TP value is based on MAP and
RPM).
Stuck Low–
f MAP value is below 50 kPa.
f Actual TP value is less than the PCM's estimated TP
value (Estimated TP value is based on MAP and
RPM).
Action Taken When the DTC Sets
f The PCM will illuminate the malfunction indicator lamp
(MIL) after the second consecutive trip in which the
fault is detected.
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.
f The PCM will use a default throttle position based on
MAP and RPM.
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 P0121 will clear
after 40 consecutive warm–up cycles have occurred
without a fault.
f DTC P0121 can be cleared by using the Scan Tool's
"Clear Info" function.
D06RX045