E026

DESCRIPTION

The throttle switch is part of the ISC motor assembly. Pin B of the ISC motor 4 way weather pack connector is the throttle switch input to the ECM. The ECM provides a 4.5 to 6.0 volt signal to pin B of the ISC. When the throttle lever contacts the ISC plunger, the throttle switch closes, shorting the 4.5 to 6.0 volt signal at pin B to pin A which is a ground (closed throttle = throttle switch input voltage low).

Code E026 is designed to detect a throttle switch input that is always grounded; throttle switch never opens.

TEST CONDITIONS
1. Code E021 and E022 clear.
2. TPS greater than 14°.
3. TPS voltage less than 4.5 volts (about 80°).

FAILURE CONDITION
1. Throttle switch input to ECM grounded (throttle switch closed).

ACTION TAKEN
1. ECM turns on "Service Control System" light.
2. ECM commands BCM to display "Service Soon" message on CCDIC.
3. ECM assumes closed throttle if brake is applied and TPS is under 12°, ECM assumes open throttle when brake is off or TPS is under 12°.

Fig. 41 Trouble Code EO26 Diagnosis:

NOTES ON FAULT TREE
1. Code E026 due to throttle switch input shorted to ground or the ISC throttle switch inoperative should result in E172 not cycling. E172 will be "LO" at all times.
2. Checking for TPS reading too high. TPS fault or misadjustment that results in a reading above 14° at closed throttle will cause a false Code E026.
3. Checking for TPS too high due to TPS or TPS circuit.
4. If TPS and circuit are both OK, the ECM should be checked.

NOTE ON INTERMITTENTS
Select ECM input E172. Manipulate affected wiring and connectors and watch for throttle switch status to change. Check for intermittent ground on CKT 427.

Select ECM data ED01. Manipulate affected wiring and connectors and watch for TPS value to go above 14° at closed throttle. Tap lightly on the TPS with a pencil or pocket screwdriver. (Check for binding TPS lever, intermittent open on CKT 476 or intermittent short to 5 volts on CKT 417 at TPS.