Code 56

CIRCUIT DESCRIPTION
The mode switch supplies the TCM with input signals regarding the selector lever position (P,R,N,D,3,2, or L). The selector lever position is indicated by the state of four ON/OFF contacts. The mode switch is located on the transmission manual shaft and is fixed to the main case.

TEST DESCRIPTION
Numbers below refer to circled numbers on the diagnostic chart.
1. This test determines if the TCM is receiving the proper input signals from the automatic transmission mode switch.
2. This test determines if the TCM is decoding the input signals from the automatic transmission mode switch properly.
3. This test determines if the automatic transmission mode switch is receiving power.
4. This test determines if TPS and TPS connectors are OK.

DIAGNOSTIC AIDS
Trouble Code 56 sets when the TCM detects:

- Position "R" range with vehicle speed greater than 62 mph (100km/h).
- Position "N" or "P" range with throttle position greater than 20% percent and engine speed less than 3000 rpm.

Trouble Code 82 sets when the TCM decodes an undefined shift position.

NOTE: In all cases, first check mode switch setting, using procedures in the appropriate Workshop Manual. Ensure that the shift linkage is adjusted before continuing diagnosis. After adjustment, clear trouble codes, test drive vehicle and read trouble codes to ensure condition is repaired.

CAUTION: When Tech-1 is connected, trouble code 58 will set for no trouble on a '90 or '91 model year vehicle if TCM detects position N or P range with throttle position greater than 10 percent and ignition switched on (engine stopped).

CIRCUIT DIAGRAM

Transmission Controls (Automatic):

CODE 56 or 82 DIAGNOSTIC CHART

Part 1

Code 56 Or 82 Diagnostic Chart (Part 1):

Part 2

Code 56 Or 82 Diagnostic Chart (Part 2):