Just Lost 3rd Gear in Auto Transmission Can I Continue to Drive on the Hwy at 55 Miles Per Hour
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.
Need a replacement transmission? Get an estimate for replacement transmissions and local installation. Look up your transmission model by vehicle make and model.
What Transmission Do I Have?
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?
- Limp Mode's Protective Actions
- Example Situation
- How the Computer Determines That a Sensor is Incorrect
- What You Should Do
- Questions to Ask Yourself
What Causes Limp Mode?
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
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.
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.
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:
Need a replacement transmission? Get an estimate for replacement transmissions and local installation. Look up your transmission model by vehicle make and model.
What Transmission Do I Have?
- 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.)?
More Information by Transmission Type
| GM | Ford | Chrysler | Other Makes | Manual / Standard |
|---|---|---|---|---|
| 4L60E | 4R75E / 4R75W | 42RLE | Nissan RE5R05A | T56 |
| 4L65E | 4F27E | A604 / 41TE | Nissan RE7R01A | T45 |
| 4L80E | 4R100 | 46RE | Nissan RE4R01A | T10 |
| 4T45E | 4R44E | 47RE | Nissan CVT | AX15 |
| 4T40 | 5R55E / 5R55N | 48RE | Mercedes 722.6 | AX5 |
| 4T65E | 5R55S / 5R55W | 45RFE | Mercedes 722.9 | Jeep NSG370 |
| 4T65E-HD | 5R110W | 545RFE | Toyota AB60E | TR-3650 |
| 4T80E | 6F35 | 62TE | Toyota U241E | NV5600 |
| 5L40E | 6F50 | 65RFE | Toyota A750E | NV4500 |
| 6L80 | 6R60 | 68RFE | Toyota A750F | NV3550 |
| 6L90 | 6R80 | W5A580 / NAG1 | Toyota A340F | NV3500 |
| 6T40 | 6R140 | F4A42-1 | Toyota A340E | G56 |
| 6T45 | 10R80 | F4A42-2 | Toyota A650E | MT82 |
| 6L45 / 6L50 | AX4N / AX4S | F4A4B-1 | Toyota A541E | 5MT |
| 6T70 | AWF21 | F4A4B-4 | Toyota A246E | |
| 6T75E | CD4E | 948HP | Toyota A245E | |
| 8L90 | FNR5 | Aisin AS68RC | Toyota A140E | |
| 8L45 | TF-80SC | Aisin AS69RC | Toyota V4A51 | |
| 9T65 | GF4A-EL | ZF 5HP24 | ||
| 9T50 | JF506E | ZF 6HP19 | ||
| 10L80 | A4LD | ZF 6HP26 | ||
| Allison 1000 | C6 | ZF 8HP70 | ||
| TH400 | AODE | ZF 8HP75 | ||
| TH350 | E4OD | ZF 948HP | ||
| 700R4 | AOD | Honda BYBA | ||
| Aisin AW55-50SN | Honda MZHA | |||
| Aisin AW55-51 | Honda MKYA | |||
| Honda MZJA | ||||
| Honda MT4A | ||||
| Honda SPCA | ||||
| Honda B0YA | ||||
| Honda BZHA | ||||
| Honda B4RA | ||||
| Honda B6VA | ||||
| Honda B7TA | ||||
| Honda B7TA | ||||
| Honda B7WA | ||||
| Honda BVLA | ||||
| Honda B7XA | ||||
| Honda PN3A | ||||
| Honda BAXA | ||||
| Honda P36A | ||||
| Honda BCLA | ||||
| Honda GPPA | ||||
| Honda PGRA | ||||
| Honda BDGA | ||||
| Honda B97A | ||||
| Honda BGHA | ||||
| Honda BMXA | ||||
| Honda BVGA | ||||
| Honda SMMA | ||||
| Honda SP5A | ||||
| Honda MCVA | ||||
| Honda M6HA | ||||
| Honda MDLA | ||||
| Honda MJFA | ||||
| Honda BJFA | ||||
| Honda MJBA | ||||
| Honda MRMA | ||||
| Honda B90A | ||||
| Honda MGFA | ||||
| Honda B5SA | ||||
| Honda MDKA | ||||
| Honda MRVA | ||||
| Honda MDRA | ||||
| Honda BDKA | ||||
| Honda BYFA | ||||
| Honda BB7A |
Problems by Make & Model
| Model |
|---|
| Acura CL |
| Acura MDX |
| Acura TL |
| BMW X5 |
| Buick Enclave |
| Buick Lacrosse |
| Buick Lucerne |
| Buick Rendezvous |
| Buick Rainier |
| Buick Regal |
| Buick Terraza |
| Cadillac CTS |
| Cadillac DTS |
| Cadillac Escalade |
| Cadillac SRX |
| Cadillac STS |
| Cadillac XTS |
| Chevy Avalanche |
| Chevy Blazer |
| Chevy C1500 |
| Chevy C2500 HD |
| Chevy C3500 HD |
| Chevy Camaro |
| Chevy Cavalier |
| Chevy Cobalt |
| Chevy Colorado |
| Chevy Equinox |
| Chevy Express 1500 |
| Chevy Express 2500 |
| Chevy Express 3500 |
| Chevy Express 4500 |
| Chevy HHR |
| Chevy Impala |
| Chevy K1500 |
| Chevy K2500 Suburban |
| Chevy Malibu |
| Chevy Monte Carlo |
| Chevy S10 |
| Chevy Silverado 1500 |
| Chevy Silverado 2500 HD |
| Chevy Silverado 3500 HD |
| Chevy SSR |
| Chevy Suburban |
| Chevy Tahoe |
| Chevy Trailblazer |
| Chevy Traverse |
| Chevy Uplander |
| Chevy Venture |
| Chevy W3500 |
| Chevy W4500 |
| Chrysler 200 |
| Chrysler 300 - 300M |
| Chrysler Aspen |
| Chrysler Pacifica |
| Chrysler PT Cruiser |
| Chrysler Sebring |
| Chrysler Town & Country |
| Dodge Avenger |
| Dodge B1500 |
| Dodge B2500 |
| Dodge B3500 |
| Dodge Challenger |
| Dodge Charger |
| Dodge Dakota |
| Dodge Durango |
| Dodge Journey |
| Dodge Magnum |
| Dodge Grand Caravan |
| Dodge Nitro |
| Dodge Ram 1500 |
| Dodge Ram 2500 |
| Dodge Ram 3500 |
| Dodge Sprinter 2500 |
| Dodge Sprinter 3500 |
| Ford Crown Victoria |
| Ford E-150 |
| Ford E-250 |
| Ford E-350 |
| Ford E-450 |
| Ford Edge |
| Ford Escape |
| Ford Excursion |
| Ford Expedition |
| Ford Explorer |
| Ford F150 |
| Ford F250 |
| Ford F350 |
| Ford F450 |
| Ford F550 |
| Ford F53 Motorhome Chassis |
| Ford Five Hundred |
| Ford Flex |
| Ford Focus |
| Ford Freestar |
| Ford Fusion |
| Ford Mustang |
| Ford Police Interceptor |
| Ford Ranger |
| Ford Taurus |
| Ford Thunderbird |
| Ford Windstar |
| GMC Acadia |
| GMC C1500 |
| GMC C2500 |
| GMC C3500 |
| GMC Canyon |
| GMC Envoy |
| GMC G1500 |
| GMC G2500 |
| GMC G3500 |
| GMC K1500 |
| GMC K2500 |
| GMC Savanna 1500 |
| GMC Savanna 2500 |
| GMC Savanna 3500 |
| GMC Sierra 1500 |
| GMC Sierra 2500 HD |
| GMC Sierra 3500 HD |
| GMC Sonoma |
| GMC Suburban |
| GMC Terrain |
| GMC W3500 |
| GMC W4500 |
| GMC Yukon |
| Honda Accord |
| Honda Civic |
| Honda CR-V |
| Honda Fit |
| Honda Odyssey |
| Honda Pilot |
| Honda Ridgeline |
| Hummer H2 |
| Hummer H3 |
| Hyundai Santa Fe |
| Hyundai Elantra |
| Infiniti G35 |
| Infiniti QX4 |
| Infiniti QX56 |
| Isuzu Ascender |
| Isuzu Axiom |
| Isuzu NPR |
| Isuzu Rodeo |
| Isuzu Trooper |
| Jeep Commander |
| Jeep Grand Cherokee |
| Jeep Liberty |
| Jeep Wrangler |
| Lexus GS300 |
| Lexus GS400 |
| Lexus GX470 |
| Lexus IS300 |
| Lexus LS400 |
| Lexus LS430 |
| Lexus LX470 |
| Lexus RX300 |
| Lincoln Aviator |
| Lincoln LS |
| Lincoln Mark LT |
| Lincoln MKC |
| Lincoln MKS |
| Lincoln MKT |
| Lincoln MKX |
| Lincoln MKZ |
| Lincoln Navigator |
| Lincoln Town Car |
| Lincoln Zephyr |
| Mazda 2 |
| Mazda 3 |
| Mazda 5 |
| Mazda 6 |
| Mazda 626 |
| Mazda CX-7 |
| Mazda CX-9 |
| Mazda Tribute |
| Mercury Grand Marquis |
| Mercury Marauder |
| Mercury Mariner |
| Mercury Milan |
| Mercury Montego |
| Mercury Mountaineer |
| Mercury Sable |
| Mini Cooper |
| Nissan Altima |
| Nissan Armada |
| Nissan Frontier |
| Nissan Maxima |
| Nissan Murano |
| Nissan Pathfinder |
| Nissan Quest |
| Nissan Rogue |
| Nissan Sentra |
| Nissan Titan |
| Nissan Versa |
| Nissan Xterra |
| Pontiac Aztek |
| Pontiac Bonneville |
| Pontiac Firebird |
| Pontiac G5 |
| Pontiac G6 |
| Pontiac G8 |
| Pontiac Grand Am |
| Pontiac Grand Prix |
| Pontiac GTO |
| Pontiac Montana |
| Pontiac Torrent |
| Pontiac Vibe |
| Ram 1500 |
| Ram 2500 |
| Ram 3500 |
| Ram C/V |
| Ram Dakota |
| Saturn Aura |
| Saturn Ion |
| Saturn Outlook |
| Saturn Relay |
| Saturn Vue |
| Toyota 4Runner |
| Toyota Avalon |
| Toyota Camry |
| Toyota Corolla |
| Toyota FJ Cruiser |
| Toyota Highlander |
| Toyota Land Cruiser |
| Toyota Matrix |
| Toyota RAV4 |
| Toyota Sequoia |
| Toyota Sienna |
| Toyota Solara |
| Toyota Tacoma |
| Toyota Tundra |
| Volkswagen Jetta |
| Volkswagen Routan |
| Volvo C30 |
| Volvo C70 |
| Volvo S40 |
| Volvo S60 |
| Volvo S70 |
| Volvo S80 |
| Volvo V40 |
| Volvo V50 |
| Volvo V70 |
| Volvo XC70 |
| Volvo XC90 |
OBD2 Transmission Trouble Codes
| DTC Code |
|---|
| P0218 |
| P0702 |
| P0705 |
| P0730 |
| P0740 |
Source: https://www.transmissionrepaircostguide.com/limp-mode/
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