DTC 27

DTC 27, 28 - Gear Switches Circuits:

TCC Switches Wiring Circuit:

Circuit Description:

The gear switches are located inside the transaxie. They are normally closed, pressure operated switches. The ECM supplies 12 volts through each selected circuit to the switch. In any condition other than the specific gear application, the signal line monitors low voltage, low potential. As road speed increases, hydraulic pressure applies the specific gear clutches and the gear switch opens. At this time, the ECM monitors a high, 12 volt potential, and interprets this to indicate that gear is applied. The ECM uses the gear signals to control fuel delivery and TCC.

DTC 27 will set if:
^ CKT 232 is open (2nd gear) when the engine is first started.
OR
^ Brake not applied.
^ Throttle angle less than 20%.
^ Vehicle speed greater than 45 mph.
^ No DTC 38.
^ CKT 232 is grounded (closed switch) for 12 seconds when vehicle is operating in 3rd gear.

DTC 28 will set if:
^ CKT 438 is open (3rd gear) when the engine is first started.
OR
^ Engine running.
^ Brake not applied.
^ No DTC 38.
^ CKT 446 is grounded (closed switch) for 10 seconds when operating in 3rd gear.
DTCs 27 and 28 do not illuminate the MIL (Service Engine Soon).

Test Description: Number(s) below refer to circled number(s) on the diagnostic chart.

1. Must use a DVM. A test light will not light due to the very low current being supplied by the ECM.
2. Checks to see if circuit is grounded through the switch.
3. Checks for a good, properly operating switch and checks circuit within transaxle for an improper ground.

Diagnostic Aids:

An intermittent may be caused by a poor connection, mis-routed harness, rubbed through wire insulation, or a wire broken inside the insulation.

Check for:
^ Poor Connection at ECM pins. Inspect harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal to wire connection.
^ Mis-routed Harness. Inspect wiring harness to insure that it is not too close to high voltage wires, such as spark plug leads.
^ Damaged Harness. Inspect harness for damage. If harness appears OK, observe gear switches on Tech 1 while moving related connectors and wiring harness. A change in display would indicate the intermittent fault location.