"It went into limp mode" is the least useful sentence a 10L90 owner can say, and it is usually the first one you hear. On this transmission the phrase covers five different situations: a car stuck in Park that will not move, a car that pulls away in 2nd and never upshifts, a car held in 5th with a reduced propulsion message, a car that quit upshifting after a hard lap, and a car whose engine computer told the TCM to stop shifting. Each one has a different cause, and only two of them need the valve body out.
This guide covers the 10L90 in the cars it actually ships in: Camaro SS and ZL1, the Cadillac CT4-V, CT5-V and CT6, and the Escalade-V. GM's bulletins list the Escalade version as RPO MHO. The facts come from two GM safety recall filings with NHTSA, a GM service bulletin, the Camaro owner manual, ATRA's GEARS magazine and Sonnax, all listed at the bottom. Where something is my own bench opinion, I say so.
| What the car does | What it usually means | Where to look first |
|---|---|---|
| Stuck in Park, will not move, high line pressure | The TCM has no power | TCM fuses, powers and grounds, battery |
| Starts in 2nd, good Reverse, no upshifts | Hydraulic default: the default disable solenoid has dropped out | Solenoid feed pressure, feed limit low valve, TCM power |
| Held in 5th, service engine light, reduced propulsion message | Recall software found feed limit low valve wear | Recall status, valve body |
| Quits upshifting after hard driving, "transmission hot" message | Fluid over temperature | Fluid level, cooler lines, thermal bypass valve |
| Shifts limited, P175E stored alongside engine codes | TCM protecting itself from an engine problem | Engine codes first, misfires especially |
Limp mode 1: No TCM power, stuck in Park
Start with the easy one, because it gets misdiagnosed as a hard failure. Keith Clark's 10L diagnostic article in GEARS says it plainly: with no power to the TCM, this transmission sits in Park with high line pressure. On the shift-by-wire cars that is exactly what the driver sees. The shifter moves, the dash may complain, and the car goes nowhere.
That is not a valve body problem. Check the TCM fuses, the power and ground circuits at the TCM connector, and the battery. In my shop, the Camaros and CT5-Vs that sit under a car cover between weekend drives are the ones that show up with a tired battery and a pile of communication codes. A load test takes five minutes. Do it before anyone says the word "transmission."
Limp mode 2: The hydraulic 2nd gear default
This is the classic limp, and on the 10L90 it is built into the hydraulics, not just the software. Sonnax's Jim Dial explains the circuit. The default disable (DD) solenoid controls two valves in the upper valve body, the default enable valve and the default select valve. The DD solenoid is powered on at all times and does not turn off until a default event. When it does turn off, those two valves send pump output pressure into the exhaust backfill passages, and the A, B, C and D clutches apply through their own exhaust ports. Four clutches applied is 2nd gear in Drive, plus Reverse. That is the unit's power-down default drive.
Two newer pieces of trade coverage fill in when and why that pressure goes away. Sonnax's Jim Dial, in his May 2025 write-up on the Gen. 2 clutch regulating changes, notes that the feed limit low valve comes into play once line pressure exceeds 119 psi, and that below 120 psi the #5 boost ball stays seated against the separator plate. That is why the drop to 2nd tends to show up loaded and hot, when the TCM is asking for high line pressure. And ATRA's Steve Garrett, writing in Gears in November 2025, explains how the TCM catches it: P0747 sets when slip speed shows a clutch still carrying torque after it was commanded off, or when "startle mitigation" logic sees a clutch apply with no shift commanded. Garrett treats P0747 on these units as a mechanical and hydraulic fault, not an electrical one, with the feed limit low valve and the 1-2-3-4-5-6-R clutch regulator valve ahead of the solenoid on his list of causes. If you are sorting a harsh or soft complaint from a true limp, our 10L90 pressure control solenoid symptoms guide breaks the three patterns apart.
So a 10L90 that pulls away in 2nd and will not upshift has either lost control of the DD solenoid electrically, or lost the pressure that holds the default valves in place. That second case leads straight to the most common 10L90 limp complaint.
Limp mode 3: 5th gear only, and the recall behind it
The part that ties most of this together is the feed limit low valve. Sonnax describes two jobs for it. It sits in the boost ball circuit that controls clutch regulation, and it is also the limit valve for solenoid feed to the DD solenoid. When that bore wears, solenoid feed to the DD solenoid drops. Depending on which gear is commanded at that moment, the default valves then let the unit fall to a lower gear or bind up. Dial lists the typical complaints: a sudden drop to 2nd while shifting into 7th or 8th, or the drive wheels trying to lock. It is usually worse hot, and a stored P0747 is common. He also warns that extended driving in this condition destroys clutch packs, because the unit binds up at times.
GM's answer on the cars was safety recall N242480630, filed with NHTSA as 25V-148 on March 6, 2025. It covers 90,081 vehicles with the 10-speed: 50,147 Camaros (2020–2022), 27,097 CT5s and 2,235 CT4s (2020–2021), and 10,602 CT6s (2019–2020). GM's cause statement says excessive wear in the control valve body can cause a fluid leak and a pressure drop that makes certain valves move unexpectedly. GM logged 115 field reports of lock-up, each lasting under 150 milliseconds.
The remedy is software only. It monitors valve performance and detects the wear about 10,000 miles before a lock-up could happen. When it trips, the transmission is limited to 5th gear until the next key cycle, with a service engine light and a reduced propulsion message, because the lock-up happens on a downshift from 8th. Per Sonnax, the next key cycle lets the car start in 1st again if the transmission is still able to. That explains a Camaro SS that "only has five gears" after a recall visit: the software did its job, and the valve is still worn.
What changed in 2026 for the SUVs
GM filed a second 10-speed recall, 26V085 (GM N252536750), on February 18, 2026. It covers 43,732 2022 Tahoe, Suburban, Yukon, Yukon XL, Escalade and Escalade ESV gasoline models with the 10-speed and electronic range select, built between March and July 2022. Those trucks have the 10L80, not the 10L90, but the filing matters for anyone working on a Gen. 2 10-speed, for two reasons. First, GM says transmissions built from April to September 2022 contain unique internal hardware that may increase the wear rate in the control valve. Second, GM describes a condition where the rear wheels can stay locked until the vehicle stops, not just lock for a moment. The remedy is the same 5th-gear software. GM also states that all 2023 and later Escalade and full-size SUV models were built with the wear-detecting software already installed, and that includes the 10L90 Escalade-V.
Run the VIN on every 10-speed that comes in limping. If the software is installed and the car is stuck in 5th, you already know what the TCM found.
Limp mode 4: Heat, and the track cars
A 10L90 behind an LT4 on a road course makes heat faster than anything else in the lineup, and the owner manual acknowledges it. GM’s Camaro owner manual (2020-2022) warns that a transmission hot message may display when the fluid is too hot, that driving in that condition can damage the vehicle, and that the driver should stop and let the engine idle to cool the fluid. The message clears once the fluid cools. The manual's track section tells owners to have the transmission fluid set to the track-specific level before track use, and to change the fluid after every 15 hours of track use, with the level set or change done by a dealer. GM said the same thing to its dealers when the 10L90 (RPO MGL) arrived in the ZL1-1LE, in bulletin 19-NA-038, and added that tap-shifting on track can push transmission temperature higher.
For a street car that runs hot, go to GM bulletin 22-NA-182. The June 2024 version (Version 5) covers the 2021–2024 Escalade with RPO MHO, lists transmission overheating and high fluid temperature among its conditions, and names a twisted cooler line as the cause on low-mileage vehicles. On ETRS units (RPO MHS, MQC) a twisted line may set P27EC. If the lines are straight, GM points at the thermal bypass valve. On the 10L80, 10L90 and 10L1000 it sits inside the valve body and opens at 143°F (61°C). If that valve never opens, fluid never goes to the cooler, and the unit runs hot even on a cool day.
Check the level at temperature with the correct DEXRON ULV before you chase anything else. Low fluid on this unit causes heat and aeration at the same time, and both of them hurt pressure control. Capacities and the level-check procedure are in our 10L90 fluid type and capacity guide.
Limp mode 5: The engine told it to stop
Clark's GEARS article covers the code that sends shops down the wrong road: P175E, shift limiting active. It means the TCM has deliberately started a shift and pressure management strategy to protect the transmission, based on sensor data from the engine or transmission side. On a 10L90 the cause is usually outside the case. On the supercharged cars, a misfire is at the top of my list. Clark's other example is worth remembering: chassis code C0267, low brake fluid level, causes no upshifts in Tow/Haul, and the vehicle shifts normally once Tow/Haul is turned off.
The lesson is the same every time. Scan every module, not just the TCM, and fix the engine and chassis codes first. A transmission replaced for a limp caused by a misfire will limp again.
A no-move right after your own valve body job
If the car came in limping and does not move at all after you had the valve body out, check your own work before the parts. Clark describes a no-move with P187E and/or P18AB on shift-by-wire units (RPO EPH) when the park pawl actuator piston is missing or not engaged. The park pawl actuator lever goes fully forward in the Park position, the piston servo opening slot must be vertical, and the valve body should drop into place without force. If you have to push on it, stop and look.
The diagnostic order that saves a valve body
- Get the exact behavior. Park only, 2nd only, 5th only, hot only, or shift limited. The gear it defaults to tells you which circuit to chase.
- Scan all modules. Engine and chassis codes come first. P175E is a result, not a cause.
- Check recall status: 25V-148 on Camaro and Cadillac cars, 26V085 on 2022 SUVs.
- Test the battery, charging output, and TCM powers and grounds. A TCM with no power looks like a dead transmission.
- Check fluid level at temperature with DEXRON ULV, and inspect the cooler lines per 22-NA-182.
- Road test cold, then hot. Normal when cold and default when hot fits feed limit low wear.
- Vacuum test the feed limit low valve. Sonnax says to test the balance end, where it wears most, and expect 18 in-Hg or higher. The reading should match the feed limit high valve, which is the same valve train with a different spring.
The repair
For a 5th-gear limp or a hot drop to 2nd on a Gen. 2 10L90, the fix is the feed limit low valve, which does not always mean a new valve body. Sonnax's drop-in kit 105740-54K covers the 10L1000 and the Gen. 2 10L60, 10L80 and 10L90. 105740-59K is the oversized version for a bore too worn for a drop-in. If the car was driven for weeks in default and binding up, pull the pan and look at the debris before you commit to a valve body repair alone. Burnt clutch material in the pan means the clutch packs paid for the delay, and the job just got bigger.
Our 10L80 limp mode guide goes deeper on the P0747 set criteria and the steel feed limit valve GM released for the 10L1000. The mechanism is the same on the 10L90.
10L90 Sonnax Feed Limit Low Valve Kit 105740-54K
The drop-in repair for the worn valve behind the 5th-gear limp, the hot drop to 2nd and P0747 on Gen. 2 10L90 valve bodies. No new valve body needed if the bore tests good.
See the 10L90 feed limit low valve kit →FAQ
Why is my 10L90 stuck in 5th gear?
On a 2020-2022 Camaro or a 2019-2021 Cadillac CT4, CT5 or CT6 it is usually the recall software working as designed. GM recall N242480630 (NHTSA 25V-148) installs TCM software that detects feed limit low valve wear about 10,000 miles before a wheel lock-up could occur, then limits the transmission to 5th gear with a service engine light and reduced propulsion message. The valve is still worn, so the car needs valve body service, not just a code clear.
Why does my 10L90 start in 2nd and not upshift?
That is the hydraulic default. Per Sonnax, when the default disable solenoid turns off, the default enable and default select valves route pump pressure through the exhaust backfill circuit and apply the A, B, C and D clutches, which is 2nd gear plus Reverse. It happens when the TCM loses control of that solenoid or when a worn feed limit low valve starves its feed pressure, which is usually worse hot.
Can overheating put a 10L90 in limp mode?
Yes. The Camaro owner manual says a transmission hot message can display when the fluid is too hot, and tells the driver to stop and idle until it clears. GM bulletin 22-NA-182 names a twisted cooler line as a cause of overheating on low-mileage vehicles and notes that the 10L90 thermal bypass valve sits inside the valve body and opens at 143 degrees F (61 degrees C).
Will clearing codes get a 10L90 out of limp mode?
It may give gears back until the fault repeats, and that is the trap. Sonnax warns that driving a unit with feed limit low valve wear destroys clutch packs because it binds up at times. Scan every module, check recall status, test the battery and fluid level, and fix the cause before the car is driven again.
Sources
- NHTSA — Part 573 Safety Recall Report 25V-148, General Motors LLC (GM recall N242480630), submitted March 6, 2025. Backs the 90,081 covered 10-speed vehicles and the per-model counts (50,147 2020–2022 Camaro, 27,097 2020–2021 CT5, 2,235 2020–2021 CT4, 10,602 2019–2020 CT6); the cause statement of control valve body wear causing a leak and pressure drop that moves valves unexpectedly; the 115 field reports and lock-up under 150 ms; and the remedy software that detects wear about 10,000 miles early and limits the transmission to 5th gear with a service engine light and reduced propulsion message, because lock-up occurs on a downshift from 8th. View source (PDF)
- NHTSA — Part 573 Safety Recall Report 26V085, General Motors LLC (GM recall N252536750), submitted February 18, 2026. Backs the 43,732 2022 Tahoe, Suburban, Yukon, Yukon XL, Escalade and Escalade ESV gasoline models with the 10-speed and ETRS; the unique internal hardware in transmissions built April to September 2022 that may increase valve wear; the condition where the rear wheels may remain locked until the vehicle stops; the same 5th-gear software remedy; and all 2023 and later models being built with the wear-detecting software. View source (PDF)
- Sonnax — Jim Dial, “Understanding the ’19-Later GM 10-Speed Safety Recall.” Backs the feed limit low valve's dual role in the boost ball circuit and as the solenoid feed limit for the default disable solenoid; the default enable and default select valves; the DD solenoid staying powered on until a default event; the A, B, C and D clutches applying through exhaust ports for a 2nd gear default plus Reverse; the drop to 2nd from 7th or 8th, the lock-up complaint, heat dependence and P0747; the warning that extended driving destroys clutch packs; the 1st gear start on the next key cycle after the recall software trips; the 18 in-Hg vacuum test; and kits 105740-54K and 105740-59K. View source
- GEARS Magazine (ATRA) — Keith Clark, “Diagnosing the 10L Series Transmission.” Backs the no-TCM-power condition of sitting in Park with high line pressure; P175E shift limiting active as a protective strategy triggered by engine or transmission sensor data; chassis code C0267 causing no upshifts in Tow/Haul; and the shift-by-wire (RPO EPH) no-move with P187E and/or P18AB from a missing or unengaged park pawl actuator piston, with the correct valve body installation sequence. View source
- General Motors — 2022 Chevrolet Camaro Owner Manual. Backs the transmission hot message and the instruction to stop and idle the engine until it clears, the track-specific transmission fluid level set before track use, and the fluid change after every 15 hours of track use, performed by a dealer (same wording as the 2020 manual). View source (PDF)
- General Motors Service Bulletin 19-NA-038 (February 2019), “2019 Camaro ZL1-1LE with 10-Speed Automatic Transmission New Model Features” (via NHTSA). Backs the 10L90 (RPO MGL) track-specific fluid level set before track use, dealer-only level set or change, the 15-hour track fluid change, and GM’s caution that tap-shifting on track can raise transmission temperature. View source (PDF)
- General Motors — Service Bulletin 22-NA-182, June 2024, Version 5 (NHTSA-hosted). Backs coverage of the 2021–2024 Escalade with RPO MHO, transmission overheating and high fluid temperature in the condition list, the twisted cooler line cause on low-mileage vehicles, P27EC on ETRS units (MHS, MQC), and the 10-speed thermal bypass valve inside the valve body opening at 143°F (61°C). View source (PDF)
- Sonnax — Jim Dial, “Understanding ’19-Later GM 10-Speed Clutch Regulating Changes” (May 6, 2025). Backs the Gen. 2 feed limit low and high valves replacing the latch valves, the feed limit low valve operating above 119 psi line pressure, and the #5 boost ball staying seated below 120 psi. View source
- GEARS Magazine (ATRA) — Steve Garrett, “Checking Out Your Seat Belt to See How Well It Works: P0747 on GM 10-Speed Applications” (Nov. 3, 2025). Backs P0747 as a mechanical/hydraulic fault on GM 10-speeds, the shift-time slip-speed and steady-state startle mitigation set logic, and the cause list led by the feed limit low valve and the 1-2-3-4-5-6-R clutch regulator valve. View source