15 Relay Output Always OFF

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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-in" mode. The relay output is fed back to the TCM through pins 16 and 17.

After a controller reset (ignition key turned to the "run" position or after cranking engine), the controller energizes the relay. Prior to this, the TCM verifies that the contacts are open by checking for no voltage at the switched battery terminals. After the relay is energized, the TCM monitors the terminals to verify that the voltage is greater than 3 volts.

This code is set when less than 3 volts are present at the Transmission Control Relay output terminals. This is measured at the Transmission Control Module (TCM) when the TCM has energized 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 run for more than two minutes
- 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:
On 93-95 MY vehicles, relay outputs only checked for 1 second after start up. Consequently, if relay output is lost after that period, the transmission will go into limp-in mode with no DTC's. Beginning with 1996 MY vehicles, relay output is always sensed, therefore anytime the switched battery drops below 3 volts, the transmission goes into limp-in mode and sets the code.

All MY's and calibrations - Relay open limp-in mode.

POSSIBLE CAUSES:
- Relay failure (intermittent relay function caused by oxidized or contaminated relay contacts)
- Short to ground or open circuit in the transmission control relay circuit(s)
- TCM connector problem
- Defective TCM