Why won't my automatic transmission shift? Limp mode

TSS parts for a transmission that won't shift: shift solenoid kit, speed sensor and internal harness

In short

It isn't always a fault: when cold, in manual mode, with O/D OFF or on hills, the transmission can hold a gear on purpose, and a CVT has no shifts to feel.
If it's stuck in one gear, usually 2nd or 3rd, with hard shifts, it's limp mode: the computer detected a fault and is protecting the transmission.
You can drive it, but per VW only "at low speeds and not in all gears", sometimes without Reverse, and it should get to a shop soon.
Typical causes are speed sensors, the range sensor, solenoids, connectors and harnesses, low voltage or the computer; check connectors and wiring first.
A key cycle can clear it for a while but doesn't fix it: real adaptive resets are done with the manufacturer's scan tool.

If your automatic car won't shift past 2nd or 3rd, slams into gear or shows a limp mode warning, the transmission computer has probably detected a fault. This article covers when it's normal for it not to shift, what limp mode is and which gear each transmission holds, whether you can keep driving, which sensors and parts cause it, which codes show up and how it's really reset.

First: is it really a fault?

Manufacturers' owner manuals describe several cases where the transmission holds a gear on purpose:

When cold: GM says that in very low temperatures shifts may be delayed until the engine warms up, and that the difference is normal.
In manual mode or in 3, 2 or L: the transmission stays in the gear you chose. Ford explains that in SelectShift it won't upshift by itself, and GM that it won't allow an upshift if speed or rpm are too low.
On hills, in heat or at altitude, or in Tow/Haul or Sport: the transmission may run a lower gear or delay shifts, and GM says it's operating normally.
With the O/D OFF button: it won't use the top gear. A steady O/D OFF light means you turned it off; if it flashes, Ford says there's a fault and to have it serviced soon.
In a CVT: there are no shifts to feel, because the ratio changes without steps.
After a battery change or a repair: the transmission relearns and, according to Ford, it may shift firmly at first.

What is transmission limp mode?

It's a built-in protection, not the fault itself. When the computer detects a problem, it holds the transmission in a fixed gear, usually with maximum line pressure and no converter lockup, so the car can still move to a safe place or a shop. That's why shifts feel hard and the car pulls away weakly. Park, Reverse and Neutral usually still work, and the check engine light may or may not come on: on the 01M, for example, VW documents limp mode without the warning lamp. Each transmission has its own limp gear:

Transmission	In limp mode
4L60E: Silverado, Tahoe, Suburban	Per GM, 2nd if it loses the speed sensor signal, or 3rd if the shift solenoid B circuit fails, with maximum pressure
6R80: F-150, Expedition, Mustang	3rd or 5th, depending on the gear it was in; after a restart, 3rd. P, R and N work
4F27E: Focus, Transit Connect	Per ATSG, 3rd in every forward range, with maximum line pressure; P, R and N work
41TE and 62TE: Caravan, Journey, PT Cruiser	2nd on the 4-speed and 3rd on the 6-speed; P, R and N work
01M: Jetta, Golf, New Beetle	3rd, or a combination of 2nd and 3rd
09G: Jetta, Beetle, Golf	Pulls away in 3rd; if already in 4th, 5th or 6th, it holds that gear until Neutral or engine off. Reverse works
Recent VW Jetta, Tiguan and others (Tiptronic or DSG)	Per VW, low speed and not all gears, and sometimes no Reverse
Nissan RE4F03: Versa, Sentra, March	3rd, even with the lever in 1, 2 or D; per Nissan, hard driving can trigger it with no fault
Nissan CVT	Per Nissan, with heat protection or fail-safe operation, vehicle speed may be gradually reduced

Can you drive in transmission limp mode?

Yes, but not far and not fast. VW's manuals say that when all the selector positions are highlighted in the instrument cluster, the transmission is running an emergency program: the car can still be driven, but at low speed and not in all gears, and in some cases Reverse may not be available; VW says to have it checked as soon as possible. If the transmission warning light is red, VW's instruction is not to continue driving. SEAT's English manual lists messages such as "Gearbox: System fault! You may continue driving", "You can continue driving with restrictions. Reverse gear disabled", "You can continue driving in D until switching off the engine" (stop somewhere safe away from traffic) and "Fault! Stop the vehicle and place the lever in the position P". Driving a long time in limp mode wears the clutches.

Which sensor can stop a transmission from shifting?

The computer decides shifts from several sensor signals. When it loses one, it substitutes a value or puts the transmission in limp mode. These are the most common culprits:

Output speed sensor: without its signal the transmission holds a fixed gear, and on many cars the speedometer drops to 0 because it uses the same signal. On the 6R80, Ford documented trucks that started in 5th with the speedometer at 0.
Turbine speed sensor (TSS): the computer compares it with the output sensor to calculate each gear ratio. We explain it in Transmission TSS sensor.
Range sensor (the shifter position): if it fails, the transmission can go into limp mode, and on some, like the 6R80, the engine won't crank either.
Fluid temperature sensor: depending on the maker, it holds a gear or makes shifts harder.
Voltage: GM warns that low voltage may keep the solenoids from working properly and cause erratic operation. Check the battery and alternator.
Communication between computers (code U0101): sometimes a wire or connector, and in a Chrysler bulletin it was fixed with engine computer software.

Before replacing a sensor, check its connector and wiring. GM, Hyundai and Ford have bulletins where the problem was the harness or connector, and TransGo sums it up for the 41TE: most often the connection or the wires are bad, not the sensor. Sun Transmissions covers speed sensor failures and code P0720 and code P0705.

Other causes: solenoids, connectors, computer and fluid

Shift solenoids: on the 4L60E, if the shift solenoid B circuit fails, it stays in 3rd. Codes P0750 to P0774 are the shift solenoids, and which one is "A" depends on the maker.
Wet or corroded connectors: Chrysler documented a corroded harness that left the 41TE in 2nd; on the 5R55W, water in the connector makes the warning light flash; and on the 4R70W, a case connector with loose terminals left the solenoids without power.
The computer: rarely the first suspect. VW says not to replace it without the repair manual's diagnosis, and GM says not to replace the module for a P0700.
Fluid level: on the 01M, VW says to check it before the sensors, clutches or valve body.
Mechanical faults: slipping clutches or a sticking valve also set codes and limp mode. If it also slips or shifts hard, read Why does my automatic transmission slip or shift hard?.

Why does it stay in 3rd after a restart?

Because many transmissions have two limp gears: one if the fault happens at speed and another after restarting. On the 6R80, per Ford's workshop manual, a fault in 1st to 3rd defaults to 3rd and one in 4th to 6th to 5th, held until Reverse, Park or a restart; after that, it defaults to 3rd. GM documents the same on other 6-speeds, and VW's 09G does something similar: it holds 4th, 5th or 6th until Neutral or engine off, then pulls away in 3rd.

How do you reset an automatic transmission?

Turning the car off and on can clear limp mode for a while. Nissan's manuals say that if fail-safe was triggered by extreme conditions, turn the ignition off, wait a few seconds and turn it back on (10 on the CVT Sentra; 3, with the lever in P, on the 4-speed Versa and March in Mexico), and have it checked if it doesn't return to normal; Chrysler recommends seeing a dealer even if the transmission resets. That doesn't fix anything: if the cause remains, the fault comes back.

Clearing what the transmission has learned is shop work, with the maker's scan tool or an equivalent: GM uses its Service Fast Learn, Chrysler its Quick Learn, VW basic settings, Nissan CONSULT and Toyota Techstream. On some Fords, disconnecting the battery clears the learned data and the transmission relearns on its own, shifting firmly at first, but that doesn't fix a fault either; and GM warns that on high-mileage units an adapt reset improves shifts only for a limited time. Watch out for a common trick: we found no manufacturer saying that flooring the accelerator with the key on resets the transmission; that sequence appears in GM and Chrysler manuals, but to reset the oil-change reminder. Sun Transmissions explains why a transmission needs to learn after a repair.

Trouble codes when it won't shift

Code	What it means	What to check
P0700	Transmission warning	Read the code stored in the transmission computer; GM says not to replace the module for this code
P0705 to P0709	Range sensor	Connector, shift cable adjustment and the sensor
P0715 to P0717	Turbine sensor (TSS)	Connector and wiring before the sensor
P0720 to P0723	Output sensor (OSS)	Connector, harness and sensor; if the speedometer reads 0, start here
P0730 to P0735	Incorrect gear ratio	Fluid level and clutches; sometimes software or a false code
P0750 to P0774	Shift solenoids	Circuit, connector and internal harness before the solenoid
P0562	Low voltage	Battery, alternator and grounds
U0101	No communication with the TCM	Connectors, network wiring and software

Sun Transmissions has articles on codes P0700, P0715, P0730 and P0750.

How it's diagnosed and repaired

Rule out the normal cases: manual mode, O/D OFF, Tow/Haul, cold weather or a CVT.
Scan it with a tool that reads the transmission computer, not just the engine: many transmission codes don't turn on the check engine light.
Check the fluid level, the battery and the alternator.
Check connectors and harnesses before replacing sensors, solenoids or the computer.
After the repair, run the relearn with a scan tool if the transmission requires it.
Don't drive far in limp mode: slowly, to a safe place or a shop.

See TSS solenoids, sensors and harnesses

TSS parts for a transmission that won't shift

The TSS catalog has electrical and control parts for the most common transmissions:

Solenoids: 4L60E shift solenoid A and B kits, 09G N88 and N89 solenoids, the 01M solenoid kit and the A604 solenoid pack.
Input and output speed sensors, such as those for the 4R75E and 5R55W.
Internal harnesses, such as the 4L60E's and the 09G's with its temperature sensor.
Pressure and range switches, and valve bodies.

Before ordering, confirm your transmission by year, engine and VIN.

TSS is an aftermarket brand with OEM-comparable quality and quality control on every product. You can buy it from our authorized distributors: in the United States from Sun Transmissions, and in Mexico the full TSS catalog at Transmisiones Veinte 07.

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