P27C5

Code

Generic P — Powertrain

Pressure Control Solenoid P Control Circuit/Open

Brand: Generic

Type: P — Powertrain

Views: UK: 26 EN: 38 RU: 33

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Page language: EN

Causes

Open or broken wiring in solenoid P circuit (connector to TCM)
Corroded or loose connector or pin at solenoid or TCM
Failed pressure control solenoid P (coil open or internal fault)
Blown fuse or loss of power/ground to transmission solenoid circuit
High resistance due to damaged insulation, pinched harness, or terminal corrosion
Faulty TCM/transmission control driver (less common)

Symptoms

MIL (check engine light) illuminated and transmission fault stored
Transmission may enter limp/backup mode (reduced shift schedule)
Harsh, delayed, or missing gear shifts
Transmission slipping or inability to hold selected gear
Possible diagnostic trouble codes for other shift/pressure solenoids or TCM faults

What to check

Read freeze frame and all transmission/TCM codes with a capable scan tool
Visually inspect wiring harness and connector for corrosion, bent pins, heat damage, chafing, or disconnection
Check related fuses and transmission power/ground circuits
Backprobe solenoid P connector at rest and while commanding with scan tool
Measure solenoid coil resistance with multimeter at connector (unplugged)
Wiggle harness and connector while monitoring for intermittent changes in code or live data

Signal parameters

Typical coil resistance (solenoid disconnected): about 10–50 ohms (manufacturer-dependent) — an open infinite reading indicates a failed coil
Supply voltage to solenoid (key on): ~12 V supply present at harness/power pin (verify)
Ground continuity to TCM ground: near 0 ohms
Commanded signal: PWM duty cycle 0–100% when commanded by TCM; frequency usually 50–250 Hz depending on vehicle
When commanded on, voltage at solenoid connector will show a PWM pattern rather than steady 12 V

Diagnostic algorithm

Use a scan tool to read P27C5 and any related transmission codes; note freeze-frame data and test-drive conditions when the code set.
Visually inspect solenoid P connector and wiring along the harness for damage, corrosion, or disconnected pins. Repair any obvious damage.
With ignition off, disconnect solenoid connector and measure coil resistance across the solenoid terminals. Compare to expected range; open/infinite = replace solenoid.
With ignition on, verify battery voltage at solenoid power pin and check for good ground continuity at ground pin. Repair poor power/ground or blown fuse.
Backprobe the solenoid connector while commanding the solenoid with a scan tool: verify the TCM provides a PWM drive and that the waveform changes when commanded. No drive indicates TCM or wiring fault.
If coil resistance is correct and command waveform is present but solenoid does not actuate, replace the solenoid assembly.
If solenoid is open or shorted, replace solenoid and any damaged connectors/wiring. If wiring is intermittent or open, repair harness and terminals.
After repairs, clear codes and perform a test drive or functional test to confirm the code does not return. If code returns with good wiring and solenoid, consider TCM output driver fault and consult manufacturer procedures for TCM diagnosis/repair or replacement.

Likely causes

Damaged harness or connector at transmission solenoid P
Corroded or pushed-out terminal causing intermittent open
Failed solenoid coil (open circuit)
Blown fuse or poor ground to transmission harness

Fault status

⚠️ Status

Pressure Control Solenoid P Circuit/Open — TCM detected an open or high-resistance condition in the solenoid P electrical circuit causing loss of proper pressure control.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5-3 hours