|Code||Fault Location||Probable Cause|
|P0700|| Transmission control system -malfunction |
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What Does Code P0700 Mean?
Years ago, the automatic transmission was simply controlled hydraulically. However, much like the engine itself, the automatic transmission has been significantly upgraded, including electronic monitoring and controls for every aspect of upshifting and downshifting. Today’s automatic transmission, up to ten speeds in some cases, can shift as smoothly or as powerfully as the driver demands, all while reducing wear and maximizing fuel economy and performance.
Keeping track of the automatic transmission is the transmission control module (TCM), which may or may not be integrated in the engine control module (ECM), depending on vehicle. The TCM shares a number of signals with the ECM, such as engine speed (rpm) and throttle position (TPS), as well as a number of other signals, such as vehicle speed (VS or WSS), gear position, shift lever position, and shaft speed sensors. Using this sensor information, the TCM activates solenoid valves related to such automatic transmission components as clutches, brakes, torque converter lock, or pressure regulator.
If there is an automatic transmission control system fault, a transmission-specific DTC (diagnostic trouble code) will set in the TCM. Since there is no “Check Transmission Light,” the ECM sets an informational DTC P0700 and illuminates the MIL or CEL (malfunction indicator lamp or check engine light). Since DTC P0700 simply refers to a fault in the TCM, further diagnosis is necessary to determine the TCM DTC and the nature of the fault. Some scan tools may or may not be able to read TCM DTCs, depending on whether the automaker has opened them up to generic readers.
What are the common causes of code P0700 ?
Depending on year, make, and model, DTC P0700 may have number of causes. Here are some of the most common.
- Electrical Problems – As with all systems in the modern automobile, electrical and electronic signals need good wiring for proper transmission. Any fault, such as rodent damage, a disconnected connector, or corrosion, can interrupt these signals, leading to transmission control failures. (User Glen reports that speed bumps tend to loosen transmission relays and connectors on some Dodge/RAM/Chrysler vehicles.)
- Truck Oversize Tire Upgrade – The ECM and TCM are programmed, from the factory, taking into account a certain range of tire sizes. Upgrading to oversized off-road tires, for example, throws off the results that the modules are expecting, which they interpret as a fault.
- Worn Automatic Transmission – Everything wears out over time, which means that automatic transmission hydraulic clutches and brakes, sprag clutches, solenoids, and valves, can fail. Hydraulic fluid may slip past worn seals, brakes and clutches may slip, and solenoids can die, any or all of which can lead to a control failure.
- Chrysler Weak Battery – Some Dodge, Jeep, Chrysler ECM and TCM are particularly vulnerable to low voltage conditions. If the battery is weak, the system may interpret this as a failure, even if the car starts on its own. Make sure you have a good battery, 12.6 V minimum, and that the generator is working properly, at least 13.6 V when idling.
- Recent Repairs – Some modern ECM-TCM combinations cannot be mixed and matched. Replacing a TCM, even if it’s specified for your specific vehicle, may need to be programmed to work with yours, so it properly communicates with the rest of the system.
- Low ATF Level – Automatic Transmission Fluid is the life-blood of your transmission. Low fluid levels can lead to lack of pressure, so if the TCM commands a solenoid to close, there may be insufficient pressure to clamp a brake, for example. The result is that the brake slips, which the TCM detects as a fault.
- Specific Driving Conditions – Depending on road conditions, particularly slippery conditions, the TCM may interpret spinning tires as a transmission control fault. If you’ve been in the slow or off-roading, simply resetting the code may be the solution, as long as your adventures didn’t ruin anything else.
What are the symptoms of code P0700 ?
Aside from the MIL, and depending on the nature of the TCM failure, you may or may not notice any drivability problems. At a minimum, you’ll likely notice a drop in fuel economy. Most commonly, you’ll notice that the automatic transmission doesn’t seems to shift properly, perhaps taking too long to get into a certain gear, or harsh gear engagement it does shift. The automatic transmission may have a hard time maintaining the right gear, failing to downshift one acceleration, for example, or taking too long to upshift when speed would normally warrant it.
In some cases, the automatic transmission can cause major drivability issues, such as stalling the engine when coming to a stop, or it may induce engine misfire-like symptoms, such as rough idle or poor acceleration. Major failures in the automatic transmission may lock out certain gears, so you may be left with 1st and Reverse, for example.
How do you troubleshoot code P0700 ?
Codes Related to P0700
If DTC P0700 is set in the ECM, look for other TCM-related DTCs to continue your diagnosis of the failure. Related ECM P-codes may include, but is certainly not limited to, the following:
- P0218 Transmission Over Temperature Condition
- P0613 TCM Processor
- P0614 ECM/TCM Incompatible
- P0706 Transmission Range Sensor Circuit Range/Performance
- P0715 Input/Turbine Speed Sensor Circuit Malfunction
- P0720 Output Speed Sensor Circuit Malfunction
- P0729 Gear Ratio Error in 6th Gear
- P0730 Incorrect Gear Ratio Error
- P0731 Gear Ratio Error in 1st Gear
- P0732 Gear Ratio Error in 2nd Gear
- P0733 Gear Ratio Error in 3rd Gear
- P0734 Gear Ratio Error in 4th Gear
- P0735 Gear Ratio Error in 5th Gear
- P0736 Gear Ratio Error in Reverse
- P0740 Torque Converter Clutch Circuit Malfunction
- P0750 Shift Solenoid A Malfunction
- P0755 Shift Solenoid B Malfunction
- P0760 Shift Solenoid C Malfunction
- P0765 Shift Solenoid D Malfunction
- P0770 Shift Solenoid E Malfunction
Newer vehicles, using the CAN (Controller Area Network) protocol, may have the following communications DTCs set, which would indicate a fault in proper communication between the ECM, TCM, and other modules in the vehicle. These may include:
- U0101 Lost Communication With Transmission Control Module
When diagnosing DTC P0700, take your time. Automatic transmissions can be notoriously finicky when it comes to identifying their faults.