20 Transmission Control Relay Output

Part 1 Of 3:

Part 2 Of 3:

Part 3 Of 3:

THEORY OF OPERATION:
The Transmission Control Relay is used to supply power to the solenoid pack when the transmission is in normal operating mode. When the relay is "off", no power is supplied to the solenoid pack and the transmission is in "limp-mode." The relay output is fed back to the TCM through pins 16 and 17.

Immediately after a controller reset (ignition key turned to the "run" position or after cranking engine), the TCM verifies that the relay contacts are open by checking for no voltage at Transmission Control Relay output terminals. After this is verified, the voltage at the solenoid pack pressure switches is checked. There should be no voltage on the pressure switches at this time. The TCM then activates the relay.

This code is set if the Transmission Control Module (TCM) senses voltage on any of the pressure switch inputs prior to the TCM energizing the relay.

LIMP-IN:
YES

WHEN MONITORED/SET CONDITIONS:
Ignition key is turned from "off" position to "run" position and/or ignition key is turned from "crank" position to "run" position. The following conditions must be met for a successful OBDII trip:
- The engine must run for more than two minutes
- The turbine speed must be greater than 600 RPM or the output speed must be greater than 400 RPM
- If the transmission is below normal operating temperature, all forward gears must be applied for 3.5 seconds each and the transmission must be in either "park" or "neutral" for 3.5 seconds
- If the transmission is hot, all forward gears must be applied for 1.5 seconds each and the transmission must be in either "park" or "neutral" for 1.5 seconds
- No MIL lamp trouble codes have occurred or recurred

TRANSMISSION EFFECTS:
All model years and calibrations - Relay open limp-in mode.

POSSIBLE CAUSES:
- Short to battery on one or more pressure switch sense circuits
- TCM connector problem
- Defective TCM