P27EC on 2021-2025 Cadillac Escalade ESV — Transmission Range Control Valve 1 Position Switch Performance
1 vehicles · 1 makes
Most Reported On
P27EC is an OBD-II diagnostic trouble code meaning “Transmission Range Control Valve 1 Position Switch Performance.” A General Motors code found on vehicles with ETRS (Electronic Transmission Range Select), GM's shift-by-wire system — commonly the 9T-family transmissions. It is also written as "Range Mode Control Valve 1 Position Switch Performance" in some references, so confirm the wording your scan tool returns. The TCM found the range control valve's position switch not reporting the commanded position — the hydraulic valve that selects Park/Reverse/Neutral/Drive is not moving to or holding position. Expect a range-selection or "shift to park" message, possible failure to leave Park, or the transmission defaulting to a safe range. It commonly appears alongside P27F0 (range control valve 2). This code is most commonly reported on 2021-2025 Cadillac Escalade ESV.
Common Causes
Diagnostic Tools
This is a powertrain code, so a basic OBD-II reader can read it. These read P27EC.
ANCEL AD310 Classic OBD-II Scanner
by ANCEL
A simple code reader for engine (P) codes on many compatible OBD-II vehicles. It does not support every vehicle or hybrid/EV application, and it does NOT read body, chassis or network codes; confirm exact-vehicle compatibility before buying.
- Read & clear engine (P) codes
- View freeze frame data
- I/M readiness status
- No batteries or app needed
BlueDriver Pro Bluetooth Scanner
by BlueDriver
Bluetooth scanner with a companion app that reads beyond the engine module — ABS, SRS and transmission — plus manufacturer-specific codes on many vehicles.
- Enhanced diagnostics (ABS, SRS, transmission)
- Repair Reports with verified fixes
- Smog check readiness
- Free app (iOS & Android)
LAUNCH CRP123X V3.0 Elite OBD-II Scanner
by LAUNCH
Handheld scanner covering the four major systems (engine, transmission, ABS, SRS) with live data streaming and graphing.
- Engine, transmission, ABS, SRS diagnostics
- Live data stream & graphing
- AutoVIN for vehicle identification
- Free lifetime updates via Wi-Fi
Autel MaxiCOM MK808S Diagnostic Tool
by Autel
Shop-level tablet with all-system coverage and bi-directional control, so you can command a module rather than only read it.
- All-system diagnostics (25+ modules)
- Bi-directional control & active tests
- Oil reset, EPB, BMS, TPMS, injector coding
- 7-inch touchscreen with Android OS
What you can do yourself, and what needs a shop
Reading the code, clearing it, and watching whether it returns is a driveway job with the right scanner. These steps are not:
- Module programming or software updates — needs the manufacturer software or a J2534 pass-through with a paid subscription.
- Replacing a control module — most are VIN-programmed and immobilizer-registered, so a new one does nothing until it is coded to your car.
- Airbag/SRS component work — a stored fault can deploy a live device.
If the vehicle is still under warranty, check for an open recall or technical service bulletin before buying anything — the repair may already be covered.
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FAQ
What does P27EC mean?
P27EC stands for "Transmission Range Control Valve 1 Position Switch Performance." A General Motors code found on vehicles with ETRS (Electronic Transmission Range Select), GM's shift-by-wire system — commonly the 9T-family transmissions. It is also written as "Range Mode Control Valve 1 Position Switch Performance" in some references, so confirm the wording your scan tool returns. The TCM found the range control valve's position switch not reporting the commanded position — the hydraulic valve that selects Park/Reverse/Neutral/Drive is not moving to or holding position. Expect a range-selection or "shift to park" message, possible failure to leave Park, or the transmission defaulting to a safe range. It commonly appears alongside P27F0 (range control valve 2).
What are the most common causes of P27EC?
The most common causes of P27EC are: Sticking or binding range control valve in the control valve body, Debris or varnish in the valve bore from contaminated transmission fluid, A kinked or twisted transmission cooler line raising back-pressure (a documented GM cause on ETRS transmissions), Incorrect transmission fluid level or degraded fluid, Auxiliary transmission pump or its harness failing on some late applications (can set P27EC before P2797), Internal transmission harness or position-switch wiring fault — verify before condemning the valve body, Failed solenoid body / control valve body assembly (GM repairs typically replace the valve body, not the TCM). The specific cause varies by vehicle.
How much does it cost to fix P27EC?
Repair costs vary widely depending on the root cause and vehicle.
Which vehicles are affected by P27EC?
Au7o has documented P27EC across 1 vehicle models from 1 manufacturers: Cadillac.
Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.