|Trouble Code||Fault Location||Probable Cause|
|P0737||TCM engine speed -output circuit||Wiring, TCM|
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What Does Code P0737 Mean?
P0737: TCM (transmission control module) or PCM (powertrain control module) has received an engine speed signal from the engine (turbine) speed output sensor that is either irrational, erratic, or in some way incorrect. Without a usable input speed signal the transmission cannot provide a proper shift strategy. The TCM or PCM compares input speed data with output speed data to determine shift patterns, as well as certain engine drivability functions. The typical engine speed or CKP (Crankshaft Position) sensor uses a three-wire connector but check the vehicle manufacturer’s wiring diagram to confirm the specific design of the vehicle in question. The first wire is a reference voltage signal (5-volts), the second wire is a ground wire, and the third wire will be a signal wire. As the reluctor ring passes by the electro magnetic sensor, the 5-volt reference signal is completed with the protruding metal surfaces. The recessed surfaces of the reluctor provide voltage interruptions and these interruptions are input to the PCM via the signal wire
NOTE: Whenever diagnosing a 700 series DTC (Diagnostic Trouble Code) with a transmission, transfer case or other driveline components, check for a DTC under chassis and body systems, not just under “P” or powertrain/engine or emission control type codes. Module communications DTCs are “U” codes. These are most often found when looking for DTCs under chassis or body systems. Chassis related codes are labeled “C” and body system related codes are labeled “B” codes and these can cause drivetrain issues if they affect a sensor that is also used by the heating and air conditioning system.
DTC P0737 setting parameters vary between manufacturers, most TCM/PCMs are programmed to expect engine speed to increase gradually (and not to exceed output speed) until a shift point is reached. If engine output speed fails to increase gradually, or if the PCM receives an erratic signal (or no signal at all), a code will be stored and the MIL malfunction indicator lamp may be illuminated. The MIL does not always illuminate because some vehicles may require multiple failure cycles in order for the MIL to be illuminated.
What are the common causes of code P0737 ?
- Defective engine speed sensor (CKP) crankshaft position sensor, you will have a NO-START concern is this occurs
- Defective transmission OSS output speed sensor
- Shorted, open, corroded, or damaged wiring circuits or connectors
- Defective shift solenoid/s
- Defective engine drivability sensors (especially the engine temperature sensor),
- Dirty/contaminated transmission fluid that restricts flow, or defective valve body
- Defective PCM (NOT Common)
What are the symptoms of code P0737 ?
- MIL (Malfunction Indicator Lamp [Check Engine & Service Engine Soon])lights on with stored historical P0737
- Harsh shift, failure to shift
- Decrease in fuel economy
- Speedometer may fluctuate or fail to operate
- Engine may stall when coming to a stop, engine misfire, sag, stall, or hesitation
- Output speed sensor code often accompanies this code