P27EC on Cadillac: How to Diagnose & Fix
Transmission Range Control Valve 1 Position Switch Performance
1 Cadillac model · 1 documented issue
P27EC on Cadillac by model: symptoms, diagnosis and fix
GM 22-NA-182 covers 2021-2025 Escalade ESV vehicles with L87, LM2 or LT4 engines and 10-speed automatic transmissions (GM codes MHS, MHO or MQC). A twisted cooler line can contribute to harsh shifts, shudder, surge, stall, flare or overheat; trouble code P27EC applies only to the MHS and MQC versions with electronic range select (ETRS). The bulletin does not prove a universal valve-body or solenoid failure.
Common Symptoms
- Harsh transmission shift
- Transmission shudder or surge
- Transmission flare or overheat
How to Fix
Have a technician confirm the exact engine and transmission version and read the trouble codes, inspect the cooler lines for a twist or misshapen section, correct the routing or replace a confirmed damaged line, set fluid level and evaluate the thermal bypass valve as directed. Continue normal diagnosis if the concern remains; do not buy transmission parts until the cause is confirmed.
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Sources for this issue (1)
P27EC code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does P27EC mean on a Cadillac?
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). On Cadillac it is documented across 1 model: Escalade ESV.
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 on a Cadillac?
Repair costs vary widely with the root cause and Cadillac model; each issue on this page carries its own estimate where one is published.
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Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.