Active Indicator Clearing Procedure - TM-9-2320-303-24-10228

WTEC III ELECTRONIC CONTROLS TROUBLESHOOTING MANUAL

CODE 21 XX --IAGROTTLE CODESM FAULT (Figure 54)

D THN S IC OR PW

The throttle sensor must have been recognized by autodetect or manually selected using the Pro-Link (see

WTEC III Pro-Link Manual) before these codes can be logged. See Paragraph 19 for further information.

Main code 21 indicates the throttle position sensor has been retracted or extended by its linkage into an error zone.

This may be due to a fault with the sensor, or a fault in the wiring to the sensor or to the ECU. This code may also

indicate a PWM signal problem. A PWM signal is proportional to throttle position and comes from some source

other than an analog throttle position sensor. Code 21 12 is set when the ECU receives TPS counts of 14 or less.

Code 21 23 is set when the ECU senses TPS counts of 233255. Whenever a code 21 XX condition is detected, the

system uses default throttle values and shifts will not adapt.

NOTE:

Code 21 XX in conjunction with code 33 XX or code 14 XX indicates the potential loss of common

ground wire 135 between the throttle, temperature sensor, and oil level sensor.

Main Code

Subcode

Meaning

Throttle position sensor failed low and

ECU signals throttle default value

Throttle position sensor failed high and

ECU signals a throttle default value

Active Indicator Clearing Procedure:

Power down

Manual

Self-clearing

NOTE:

Before troubleshooting, read Paragraph 56. Also, check the ECU input voltage.

Troubleshooting:

1. Plug in the DDR, select Diagnostic Data, and read throttle counts and percent. If the TPS failed

high (code 21 23), the problem may be toward the full throttle end of the TPS travel. If the TPS

failed low (code 21 12), the problem may be at the closed throttle end of the TPS travel.

NOTE:

Code 21 12 may occur when the throttle source is J1587 or J1939 and an analog throttle source is

falsely detected. This condition may be due to a problem in an unused TPS branch of a universal

external harness. To prevent this occurrence, remove wire 156 from the ECU connector and insert a

cavity plug in the space vacated by the wire. Be sure that the unused TPS branch is routed away from

potential induced voltage sources and the connector is protected from external contamination.

NOTE:

Code 21 12 can result when the +5V line (wire 124) which powers the analog sensor is shorted to

ground. Wire 124 also powers the OLS, RMR, retarder temperature sensor, sump temperature sensor,

and shift selector and is present in all three ECU connectors.

2. If counts are high but the percentage never reaches 100 percent, TPS linkage may have bound up

and overstroked the TPS to set a false 100 percent reading. After TPS overstroking ceases, the

TPS will not automatically return to 100 percent. After the TPS is correctly installed and adjusted,

use the Pro-Link to reset throttle calibration or cycle the ignition 5 times to reset the 0 percent

and 100 percent settings.

0021 0056