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P090DClutch "B" Actuator Control Circuit High

The clutch "B" actuator control circuit is reading higher than expected, typically from a short to battery voltage or an open that lets the circuit float high.

Definition

The TCM monitors the voltage on the clutch "B" actuator control circuit whenever the output is driven and when it is at rest. P090D sets when that voltage exceeds the calibrated maximum — most often a control wire shorted to battery voltage, though a broken wire or failed driver can also let a pulled-up circuit rail high. The TCM disables the output to protect the driver stage, leaving the second clutch uncontrolled: symptoms include missing or blocked gears, harsh engagement, limp-home or no-drive operation on dual-clutch transmissions, and a transmission warning lamp with a stored MIL.

Common causes

  • Actuator control wire shorted to battery voltage
  • Open circuit in the control wire allowing the monitored circuit to float high
  • Corroded or burned terminal creating an open at the actuator connector
  • Actuator winding failed open
  • Failed TCM/mechatronic output driver stuck high
  • Chafed harness crossing a power feed after collision or service work

Common misdiagnoses

  • Replacing the actuator when the harness is shorted to power
  • Replacing the TCM before wiring diagnosis
  • Replacing the transmission for a no-drive complaint
  • Blaming the battery or charging system

Troubleshooting steps

  1. 1.Check the circuit voltage at rest

    Key on with the actuator commanded off, back-probe the control wire; battery voltage present when the driver should be off indicates a short to power or a driver stuck high.

  2. 2.Isolate the short to voltage

    Disconnect the TCM and re-measure; if battery voltage remains on the wire, the harness is crossed with a power circuit — inspect areas of common routing with switched-power feeds.

  3. 3.Test for opens

    With both ends disconnected, verify end-to-end continuity of less than about 1 ohm on each control wire and inspect connector terminals for corrosion or burning that could create an open.

  4. 4.Measure actuator winding resistance

    Compare the motor or solenoid resistance to specification; an open (OL) reading means the actuator itself has failed and let the monitored circuit float.

  5. 5.Verify the module driver

    With wiring and actuator proven good, command the actuator while scoping the control circuit; a driver that never pulls the circuit toward its commanded state indicates a failed TCM output.

  6. 6.Confirm the repair

    Clear codes, run the clutch adaptation if the actuator was replaced, and road test through all gears confirming normal engagement and no reset.

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