P2705 code definition
For Ford and Chrysler makes, a P2705 trouble code indicates a malfunction in the transmission’s friction elements. The PCM has stored a trouble code and may show an illuminated malfunction indicator lamp (MIL) or Check Engine Light. Some vehicles might also be locked into “limp-in” mode.
What the P2705 trouble code means
A P2705 code is registered when the transmission’s output RPM signal is out of parameters, as compared to the input RPM signal, and the PCM reads it as a malfunction of transmission friction element. It’s not unlike a transmission component slippage code, which may accompany a P2705 code.
What causes a P2705 code
A P2705 code can be triggered by:
- Low transmission fluid level
- Transmission fluid leak
- Failing transmission pump
- Overheating engine
- Defective input or output speed sensors
- Faulty PCM
- Problems with wiring, connectors or other related electrical components
What are symptoms of a P2705 code?
- Harsh shifts
- Delayed transmission engagement
- Transmission slippage
- Illuminated MIL or Check Engine Light
- “Limp-in” mode
How does a mechanic diagnose a P2705 code?
A tech can diagnose a P2705 code with a code reader that can access sensor codes, using that data to determine when the fault occurred. A road test might also be in order. It can be easy to misdiagnose a P2705 code, since a low fluid condition can quickly cause other problems due to overheating and damage to internal transmission components.
Most OBD-II equipped vehicles have an input/turbine speed sensor that provides an input speed signal to the PCM. This sensor is usually threaded directly into the transmission housing or is bolted to the exterior of the transmission. This Hall-effect sensor sends voltage signal interruptions, which are read as a square waveform by the PCM. Transmission shift points are determined by a comparison of input and output shaft speeds.
How should a tech repair a P2705 code?
A 3-wire connector is commonly used for this sensor, with one as a 5-volt reference signal, one as a ground wire and one as signal wire. Diagnosis should begin with a visual inspection for shorted, corroded, loose or damaged connections or wires. Repair or replace as needed, then retest the system.
Check for wiring or connectors that may be contaminated from engine oil, leaking transmission fluid, damage from road debris or burns from hot exhaust pipes. Problems like this can be read as an inconsistency between input and output speed sensor readings, and can be enough for the PCM to register them as a transmission friction element problem.
A tech should have access to a factory wiring schematic while repairing this problem. Retest the system after repairs. If all wiring, connectors, fuses and other components check out, connect the scanner to collect codes and diagnose intermittent conditions. Clear the codes, drive the vehicle and see if the code returns. If not, it could be an intermittent problem that may have to be allowed to worsen before a correct diagnosis can be made.
Test any related circuits and sensors for resistance and continuity, compared against manufacturer’s specs. Connect an oscilloscope and observe real-time sensor data from input and output speed sensors. Watch for “soft spots” in the O-scope’s waveform and replace any components indicated.
Repair any transmission leaks and refill with the right type of fluid. If the unit doesn’t overheat and seems to be working fine, a faulty input or output speed sensor is probably indicated. If the old fluid smells burnt or if the unit is leaking from behind the torque converter, at the front seal, the transmission will have to be dropped. At that point, it may just be best to consider a hard-parts rebuild.
If everything else is eliminated, the PCM could be faulty – but PCM failure doesn’t happen often, and replacing the PCM will require reprogramming.
Additional notes on P2705 code
Sensor issues can be hard to track down, and often can mean several things. A methodical process-of-elimination method is key, rather than just replacing parts. One thing’s for sure, though – transmission problems only get worse as time and miles go on. A P2705 code and its symptoms mean that you should not keep driving that vehicle. Get it into a shop for qualified diagnosis and repair as soon as possible.
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