P27CF: Pressure Control Solenoid R Control Circuit Low

What it means

The control circuit for pressure control solenoid R is reporting a low electrical condition.

At a glance

• Usually lights the check-engine light
• The engine or gearbox may go into limp mode

How it works

Pressure control solenoid R is controlled electrically to regulate transmission hydraulic pressure. P27CF sets when the module detects a low electrical condition in the solenoid R control circuit, which can be caused by a short to ground, an internally shorted coil, or excessive resistance at a corroded connection.

Common causes

Most likely first.

1. Control wire shorted to ground
2. Internal short in solenoid coil
3. Connector pins corroded - high contact resistance

Symptoms

• Transmission warning light may illuminate
• Harsh or delayed shifting
• Transmission may enter limp mode

How to diagnose it

1. Record freeze-frame data and check for related transmission circuit codes to see when the low condition occurred.
2. Inspect solenoid R's connector and harness for corrosion, damaged insulation, pinched wiring, or a wire touching ground.
3. Check the solenoid R connector terminals for corrosion or poor contact that could add resistance.
4. Measure solenoid R coil resistance and compare it with the manufacturer's specification to check for an internal short.
5. Test the control wire for a short to ground and check circuit continuity using the vehicle wiring diagram.
6. If the solenoid and wiring pass, check the module-side circuit for a low condition before considering a control module fault.

Common fixes

• Clean or repair corroded solenoid R connector terminals and restore a sound connection.
• Repair wiring that is shorted to ground or has damaged insulation.
• Replace solenoid R if its coil is internally shorted or outside the manufacturer's specification.
• Repair the remaining control-circuit fault if testing locates it at the module-side wiring.

Can I keep driving?

Limit driving if shifts are harsh or delayed, or the transmission enters limp mode; avoid towing and heavy acceleration. A low solenoid R circuit condition can disrupt pressure control and worsen shifting, with continued slipping risking transmission damage.