E026

Code E26:

ISC Circuit:

DESCRIPTION:

The throttle switch is part of the ISC motor assembly. The PCM/ECM provides a 5 volt reference on CKT 427. When the throttle lever contacts the ISC plunger, the throttle switch closes. When the throttle switch is closed the input voltage is low. Code E26 sets when the PCM/ECM sees a TPS signal greater than 20 degrees (accelerator being applied) but the throttle switch remains closed.

TEST CONDITIONS:

1. Code E21 and E22 not set.
2. TPS value between 20 and 75 degrees.

FAILURE CONDITION:

Throttle switch input to PCM/ECM closed for 1.8 seconds.

ACTION TAKEN:

1. PCM/ECM turns on "SERVICE ENGINE SOON" light.
2. PCM/ECM assumes the throttle is closed if brake is applied and TPS is less than 18°.
3. PCM/ECM assumes the throttle open when brake is off or the TPS is greater than 18°.

NOTES ON FAULT TREE:

1. If the PCM/ECM does not detect that the throttle switch has opened or closed, the Fuel Data Center will display E.7.2.

2. When the PCM/ECM detects the switch open and closed the Fuel Data Center will alternately display E.7.2 and 00.

3. Checking for TPS too high due to TPS or TPS circuitry.

4. If TPS and TPS circuit are OK, the PCM/ECM should be checked per Chart C-1.

NOTE ON INTERMITTENTS:

Select PCM/ECM switch test. Manipulate ISC connector, ISC wiring, and PCM/ECM connector and observe display. If the throttle switch state changes momentarily, 00 will appear on the display. Check for intermittent opens and shorts in the TPS wiring. Manipulate TPS connector and wiring while observing PCM/ECM data P.0.1 and watch for TPS value to go above 20 degrees at throttle closed.