E028

ECM Code E028:

ECM Code E028 (Cont'd):

Transmission Circuit:

DESCRIPTION:

The third and fourth gear switches in the transmission are normally closed switches, that are opened by transmission oil pressure. The ECM sends a 12 volt signal to each of the switches. When not in third or fourth gear, the third and fourth gear inputs are grounded by the normally closed switches. When third gear is achieved, the third gear switch is opened by, third gear oil pressure and the third gear input changes from 0 volts to 12 volts. When fourth gear is achieved, the fourth gear switch is opened by fourth gear oil pressure and the fourth gear input changes from 0 to 12 volts. Code E028 is designed to detect a false third or fourth gear indication to ECM.

TEST CONDITIONS:

1. Code E024 clear.
2. Transmission in park or neutral.
3. Vehicle speed less than or equal to 4 MPH.

FAILURE CONDITION:

Third gear input to ECM not grounded or fourth gear input to ECM not grounded.

ACTION TAKEN:

1. ECM turns on "SERVICE ENGINE SOON" telltale.
2. ECM commands BCM to display "SERVICE SOON" message on CCDIC.

NOTE ON INTERMITTENTS:

At key "ON", engine "OFF", trans in park, manipulate affected wiring and connectors while observing the third/fourth gear status light. If third or fourth gear status indicator flashes on repair intermittent open in CKT 438 (third gear) or CKT 446 (fourth gear).

Review the snapshot data parameters stored with this code to verify failure condition. If the failure condition is verified, check and repair intermittent wiring connection, or sensor.