E055

Code E55:

Sensor Circuit:

DESCRIPTION:

The TPS on this engine 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 E55 will be stored in memory at the next key "ON" cycle.

NOTE: Parameter P.0.1 displays uncorrected TPS values.

TEST CONDITIONS:

1. No problems detected on the throttle position sensor or throttle switch circuits.
2. At key off the ECM will test for a misadjusted TPS, (see Discription).

FAILURE CONDITION:

"Learned" TPS is less than -2.9° or greater than +3.0°.

ACTION TAKEN:

At the next key on, the ECM will log code E55 as current. No telltale or "Service" message will appear.

NOTES ON FAULT TREE:

1. Checking TPS adjustment. ECM parameter P.O.1 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 E.7.2 and while observing ISC operation during ECM output cycling E.0.6. Manipulate TPS wiring and connector while observing ECM parameter P.O.1, TPS. Check for TPS secured to throttle body (both TORX screws tight). Cycle the TPS throuigh its full travel while observing P.O.1 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. If wiring and connector check out OK, substitute a known good TPS sensor and retest.