E055

ECM Code E055:

DFI Sensor Circuit:

DESCRIPTION:

The TPS on 1989 DFI is "self adjusting". At key-off, the ECM executes a TPS learning routine. After key off, the ECM will retract the ISC until the ISC throttle switch opens and the throttle linkage is resting on the minimum air screw. At that time, the ECM stores the TPS value and calculates a correction. If the same correction factor occurs on two consecutive key "off" cycles, the TPS is then corrected to 0 degrees using the correction factor "learned". If the value needs correction by, more than -2.9 degrees or +3.0 degrees, code E055 will be stored in memory at the next key "ON" cycle.

Note: Parameter ED01, TPS, displays uncorrected TPS values.

TEST CONDITIONS:

1. Codes E021, E022, E026, E027 clear.
2. ECM tests for code E055 at key off. At key off the ISC will retract until the throttle switch opens. The TPS value is read by the ECM and a correction factor is stored. If the correction factor value is the same on two consecutive key off cycles, the TPS setting is "relearned".

FAILURE CONDITION:

If TPS correction needed is from -10° to -2.9° or from 3.0 to 90.0° the "TPS out of adjustment" flag is set.

ACTION TAKEN:

At the next key on, the ECM will see the "TPS out of adjustment" flag and log code E055 as current. No telltale or "Service" message will appear.

NOTES ON FAULT TREE:

1. Checking TPS adjustment. ECM parameter EDO1 TPS, displays uncorrected TPS so that it can be used to check TPS adjustment.

2. TPS adjustment is OK.

3. If TPS adjustment is OK, ISC and throttle switch operation need to be thoroughly checked. The throttle linkage needs to be checked for proper operation -- throttle, cruise and TV cables not binding, proper throttle return spring operation throttle shaft and blades free to move.

NOTE ON INTERMITTENTS:

Manipulate ISC wiring while observing ECM input EI72 and while observing ISC operation during ECM output Cycling E006. Manipulate TPS wiring and connector while observing ECM parameter EDO1 for jumps, skips, intermittent behavior. Check for TPS secured to throttle body (both TORX screws tight). Cycle the TPS throuigh its full travel while observing EDO1 for erratic behavior. Check for proper part number TPS installed on vehicle. Remove and replace the TPS, ISC and ECM connectors and ensure that they are latched.