PCM turns on MIL. PCM substitutes coolant temperature value for transaxle temperature until coolant temperature reaches 221°F (105°C) then transaxle will be set to hot mode operation.

NOTE: Test numbers refer to numbers on diagnostic chart.

With transaxle temperature sensor or wiring open, PCM data PD77 will read -35°C or less. If parameter does not show this, sensor and circuit is okay.
Check for open in circuit No. 585 between PCM and sensor connector. If PCM data PD77 reads 148-151°C with sensor terminal "M" jumpered to ground, the circuit No. 585 and PCM are okay.
Checks circuit No. 452 for open to PCM terminal connector.
Checks PCM's ability to recognize low voltage on PCM terminal 1B14 (transaxle temperature sensor input). If grounding PCM terminal 1B14 caused PCM data PD77 to read 148-151°C, check for open in circuit No. 585 between PCM and sensor connector.
Checks for open transaxle temperature sensor.

Fig 1: Code P059 Schematic, Open Transaxle Temperature Sensor Circuit

Courtesy of GENERAL MOTORS CORP.

When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

• You smell fuel, burning insulation, or see smoke.

• Brakes feel soft, pull hard to one side, or make grinding noises.

• The engine overheats, stalls repeatedly, or misfires under load.

• You are missing required tools, torque specs, or safe lifting equipment.

• You are not confident in the next step or safety outcome.

Safety Warning

Code P059, Open Transaxle Temperature Sensor Circuit: Action

Use the Manual With the Right Hardware

When to See a Mechanic

Rather have a pro handle this?