What is Limp Mode? – Causes & What to Do

Picture this: you are driving along when, out of the blue, your car’s transmission starts acting up. The “check engine” light comes on, telling you that there is a problem. At the same time, your car’s transmission automatically shifts into second or third gear and stays there.

Limited to one gear and 30-45 mph, you know there is a serious problem with your car’s transmission and you have to get your car to either your dealer or transmission repair shop to have the problem diagnosed and repaired.

Naturally, the first questions that go through your head are: Why did this happen? How severe is it? and How much will it cost to fix?

In This Guide

What Causes Limp Mode?

Since the early 1980s, computers have been responsible for monitoring and controlling systems in automobiles. At first, the computer was used primarily for emissions control and fuel economy, but within a few years, many more systems were computer controlled included anti-lock braking, airbags, climate control and handling.

We know a good transmission shop in your area.

Today, nearly every system in your vehicle is operated by the computer – including the transmission’s line pressure, shift timing, sequence and feel. The vehicle speed sensor provides input to help control ABS, fuel mixture, fuel injection and transmission operation. The manifold absolute pressure (MAP) sensor and throttle position sensor (TPS) provide the engine’s load information which is used to manage the shift and downshifting in the transmission when you’re driving up an incline or you’ve put the pedal to the metal.

“Fail Code” conditions or “Limp Mode” occurs when there is a problem with the logic of a vehicle’s computer. When the signal value sent by a sensor to the computer is not within a pre-programmed range specified by the manufacturer, it will switch to “secondary” programming. These procedures are designed to protect the transmission from further damage that could be caused by the signal error.

As long as the computer is receiving signals from the MAP, TPS, vehicle speed and other sensors that fall within their “normal” ranges based on the current conditions, the transmission will operate normally. However, as mentioned above, if it receives a signal that is outside of the expected range, it will switch to secondary/emergency operation.

The exact measures taken in secondary operation is determined by the computer’s logic as programmed by the manufacturer and depends on how far outside the acceptable range the signal is (if there is any signal at all). It might react differently when the value is higher than the highest parameter than it does when the value is lower than the lowest allowable value.

Limp Mode’s Protective Actions

Check Engine Light - Limp Mode

If the signal value wasn’t far enough outside of the range to indicate a mechanical failure, the first thing the computer will do is turn the check engine light on to alert the driver that they should have the vehicle checked out using a code reader/diagnostic scanner to see if there are any “soft codes” listed. Soft codes can indicate that a low priority sensor has malfunctioned or is starting to break down. If the light goes away after restarting your car, it could mean that the sensor only failed once due to a loose connection or it could be a sign that its condition is getting worse. Critical functionality is typically unaffected by this kind of problem, but if the issue isn’t resolved, it can negatively impact the performance or fuel efficiency of the vehicle.

Need Your Transmission Repaired? A good repair shop can be hard to find – especially on short notice. We’ll have the Cost Guide Certified shop in your area give you a call with a free estimate.

Now, if the signal value from a high priority sensor (necessary for critical functions) is dangerously far out of the acceptable operating range, the computer switches over to secondary “survival” mode. This is known as a “hard code”. In this mode, the computer shuts off the electronic shift solenoids. This disables the transmission’s ability to shift gears and causes it to default to single usable gear – usually second or third. In addition, the pressure in the transmission’s fluid lines is set to high in order to protect the bands and clutches from being damaged. The signals that control the line pressure are set to “full on” to prevent the clutch pack from a slipping dangerously.

All of these changes result in the previously described “Limp Mode”. Instead of leaving you stranded with a broken down vehicle, it enables the vehicle to limp home or to the nearest service center for repairs while reducing the risk of doing further damage.

Example

For example, one of situations that would cause a transmission to go into limp mode is if the cable harness going to the transmission is damaged or detached. In this case, the computer would sense that it lost communication with the transmission, but since the harness is detached, the command to go into limp mode cannot make it to the transmission. However, with no power supplied to the solenoids, the line pressure is set to high and the transmission is stuck in 2nd or 3rd gear – the same effect the limp mode command would have.

How the Computer Determines That a Sensor is Incorrect

Say, for example, that the computer receives a signal from the Throttle Position Sensor (TPS) stating that the pedal is to the metal when the throttle is actually closed. It would spot this error when it compared this status with the vehicle speed sensor, which would be signaling low or no speed. As soon as it sees this discrepancy, the computer will command the transmission to go into limp mode and turn the check engine light on. A signal value by itself can’t always be classified as an error, but when analyzed with other sensor outputs, the computer can easily figure out if there is a problem.

Fault Code Diagnostic Scanner

The fault code of the sensor causing the error is recorded by the computer. A mechanic can use a diagnostic scanner or code reader to find the recorded codes and then look them up in a table from the manufacturer to determine which sensor, and therefore which system is the source of the malfunction. Many scanners are pre-programmed with these tables and return more information than just the codes.

For example, the diagnostic scanner could return the code “35”, which indicates that the problem has to do with the transmission fluid temperature sensor. The abnormal values that were recorded and the “normal” range for the sensor could also be provided to the mechanic.

It is recommended to have a vehicle’s computer scanned regularly for fault codes – especially if the check engine light is on. This is done by most service centers during routine tune-ups.

What You Should Do

If your transmission is in limp mode, your transmission has a problem and you should get it fixed as soon as possible. Here is what you should do:

  • Do not panic! Limp mode is specifically designed to limit further damage and allow you to get your car to a service center
  • If possible, drive directly to a service center
  • Otherwise, drive home and call a service center to have your vehicle towed
  • If you do not feel comfortable driving at a limited speed, pull off the road where it is safe to do so and call for a tow
  • It is advised that you do not continue to drive a vehicle in limp mode as it is unsafe and can cause further damage to your vehicle

Questions to Ask Yourself

Once your vehicle is safely in the service area, it is time to answer a few questions that will help diagnose the problem:

  • How fast were you driving and how long had you been driving when the problem occurred?
  • Did any lights on the dash come on? Did they come on when you started the car or after driving a while? Did they stay on?
  • What repairs or maintenance has been done to the vehicle in the last month?
  • Have you noticed any signs of a problem recently (noises, behaviors, leaks, etc.)?

Get a Diagnosis

Still not sure what the problem is? Click the green button and we’ll have the Cost Guide Certified shop in your area give you a call with a free estimate.

29 thoughts on “What is Limp Mode? – Causes & What to Do

  1. I have an 02 bmw 330i, it went in limp mode at around 35 mph, so I serviced the tranny, replaced my maf sensor, and still in limp mode. Could this just be a problem with resetting the computer?

    • we have the same problem with our BMW and cant find the problem after spending over 20 000.00 on the vehicle
      pls let me know if you solved yours

    • Hi, same issue with limp mode in 2004 320i, very low ks, just paid $$$ to have 2 x Spd sensors replaced & within 6 weeks limp mode again but bmw mechanic saying it’s another sensor!!! in the tranny!!!
      Can I just turn computer off that triggers limp mode as mech saying auto is fine,
      Thanks

  2. I have an 04 ford xr6 and while driving the car lost all gears but 1 I couldnt change to any other gear there was no lights on the dash could this be in limp mode or is the trans stuffed? It is a trick trans.

  3. I had a mechanic (whom I trust) look at my 2005 Ford Expedition for an A/C problem I was having. He found the problem to be an electrical issue and the source was probably a corroded bulkhead connector, etc. Instead of trying to take parts out, trace wires, etc, he decided it would be easier and just as effective to simply make a homemade jumper at the Compressor Clutch Relay. This worked to fix the A/C issue. However, about 10 minutes down the road, my SUV suddenly went into Limited Power (Limp) mode, the O/D dash light started blinking repeatedly, check engine dash light came on, and I couldn’t accelerate past about 30-45 mph. I turned around, took the truck back to the mechanic, we took off the jumper, and the truck stayed in Limp mode. We checked/cleared the engine codes, nothing changed. We’re thinking that we possibly fried something. Is it possible we simply fried the Compressor Clutch Relay? Would that cause Limp mode? Or did we possibly fry a computer component?

  4. I sheared the cooling fan wires completely apart,and the 05 f-350 went into the limp mode. I let the truck cool down,and made a new wire harness. I resumed driving about 100 miles to where I was going and no problems, about two hours later on my return trip, the truck just stopped running completely. Got out and checked the engine and the wires had come apart on the cooling fan again, so this time I pulled the truck the 23 miles home, then I redid the harness avsin, and had juice to everything but the ignition, it was a fuse, starts now, but won’t shift up, it actually locks the reared up when it trays to shift. I’m stumped, any thoughts on this anybody?

  5. I have a 2005 GMC Envoy with 207,000 miles on it. Yesterday while taking a turn and slowing down the car seemed to surge a little and since then while accelerating the engine is revving high but with considerably lower power and low speed. No dash lights have come on. The engine noise has become a ‘little’ whiny since today morning.
    Can someone please suggest what could be wrong here?

  6. My 2015 Dodge Durango went into limp mode when passing on highway — pulled over turned off the engine and restarted. No further problem until a couple of months later went into limp mode pulling out of day camp parking lot — 2 four year old grandchildren yelling out in the back “What is wrong with the car?’
    Brought the car (3,200 miles) to dealer — dealer said computer showed no problem; therefore, no problem. Really? left car at dealer and said I would not drive with grandkids in car until he found the problem — would he risk driving an unsafe car with this family members?

    • I have a 2008 Kia Amante. Two weeks ago, I made appt with my trusted RadAir due to car in “limp mode”. Check engine light on. RPMs would not go above 2. Slowly could increase to 60MPH. The morning of appt, my car accelerated properly, but still had diagnostic testing for
      check engine sensor. RadAir said no code showed on computer. Paid $100 for test. Car ran fine until today. Car went into limp mode again with engine light on. Even though diagnostic testing reveal no codes, shouldn’t the car be checked to rule out what caused the limp mode?
      Can an automatic car starter contribute to this problem even if it is working fine and is less than a year old. Please help.

  7. I have a 04 chevy trailblazer, I have first and reverse, I can manually shift into second. When it should shift into third it down shifts back to first. Before all this happen I was sitting and it was idling and the reduce engine power light came on. I shut it down and it was fine drove it home. Then this happened any idea what it could be. We was thing selinod, but now think maybe clutches for 3

  8. I have a 2002 honda civic and all of a sudden yesterday while we were drivinh it the transmission just acted like i had put it in neutral, i can cut tbe car off and start it back up and it will do fine for a mile maybe two then same thing happens again, and again can shut car off for just bout 10 seconds start it back and go again, what is wrong?

  9. 2008 Grand Caravan seems to be going into limp mode. Three times randomly in last five hundred miles. The last time i finally got a check engine light and it would not shift. Stopped car and shut it off, restarted still with check engine light and it shifted fine??? I had the transmission filter and oil and both speed sensors changed, (input/output) and it drove great until today when i got the check engine light and would not shift. What should be my next move….solenoid pack????????

  10. I have a 03 Acura TL type S 3.2L that works find until the oil heats up the transmition didn’t work at All , no matter in what gear do I put it. Looks like is in neutral​ but if I kill the engine and pull the key out. And put it right away back and start the engine it will work perfect for 3 or 4 minutes and is the same thing over and over so what’s my problem or I need another transmition?

  11. I had limp mode issues in my 2005 Dodge Dakota. After had my transmission solenoid replaced found the problem was just a loose and dirty battery terminal.

Leave a Comment