P0738 - OBD Trouble Code

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Oftentimes, Engine Warning Light turns up almost immediately it senses the OBD code error. This directly impacts the engine performance as it struggles with power and acceleration as well as harsh shifting with increased consumption of fuel by the engine along with engine stalling and problematic speed sensors and crankshaft sensor.

OBD-II Code P0738 is defined as a TCM Engine Speed Output Circuit Low.

The P0738 code is a standard OBD-II trouble code that identifies an issue with the signal from the engine speed output sensor in the transmission control module (TCM). Information from the engine speed output sensor is sent to the powertrain control module (PCM), which uses the data to calculate the ideal shift strategy. In general, the engine speed should increase slowly as the vehicle speed is increasing, until the proper shift point has been reached. When the PCM notes that engine speed is either increasing too quickly, or not at all, then the P0738 trouble code will be triggered. The code will also be stored if the PCM is unable to receive a signal from the engine output speed sensor.

What causes this problem with the TCM Engine Speed Output Circuit Low?

• Corroded or damaged wires and circuitry
• Corroded or loose connection to the TCM
• Defective crank sensor (CPS) and/or circuit
• Defective TCM
• Damaged pins in modules
• Low system voltage
• Engine output speed sensor faulty
• Transmission output speed sensor faulty
• Insufficient transmission fluid level
• Dirty transmission fluid

1. Crank Position Sensor - Check for faulty crankshaft position sensor and replace it as required. Buy new crank position sensor now!
2. Speed Sensor - It is important to check on speed sensor functionality and replace it, if found faulty. Buy new speed sensor now!
3. Transmission Control Module - Inspect for TCM error and circuitry and replace it now for proper performance of the transmission system. Buy new TCM components now!
4. Powertrain Control Module - P0738 error code also relates to problems with the powertrain control module. Find all the Powertrain related parts with us.
5. Engine Wiring Connectors - Check for faulty wiring and connectors and replace it as required for proper functioning of all engine components. Buy new wiring and connectors now!
6. Diagnostic Tools - It is important to use correct diagnostic tools to solve the OBD code error. Buy new tools and equipment for us!

Interested in knowing the symptoms to OBD code P0738? If yes, then you have arrived at the right place. We at Parts Avatar have listed out few common symptoms associated with this transmission system problems.

Common Symptoms

• Driveability issues
• Vehicle entering in “limp” mode
• Will not up shift (Stuck in low gear)
• Low vehicle speed
• High RPMS (Rounds Per Minute)
• Transmission slipping in and out of gear
• Poor engine performance

Here are some ways with the help of which you will be able to correct the OBD Code P0738.

• Replace or repair engine output speed sensor
• Replace or repair the transmission output speed sensor
• Replacement or addition of transmission fluid
• Replace or repair of wires, connectors, and fuses
• In rare cases, replacement of the PCM

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• The P0738 code will be diagnosed using an OBD-II trouble code scanner. A certified mechanic can use the scanner to view the freeze frame data for the code, and to check for the presence of additional trouble codes. If the mechanic notes that other trouble codes are present, then they should be addressed in the order in which they appear on the scanner.
• Then reset the trouble codes, restart the vehicle, and check to see if the P0738 code remains detected. If it does not, then it is likely an intermittent error, or possible an inaccurate detection.
• If the code remains following the reset and restart, then the mechanic should check the transmission fluid. If the fluid level is too low, then it will need to be replenished, and leaks should be carefully checked for.
• The failure to note fluid leaks can result in more severe damage down the line. If the transmission fluid is dirty, it can be flushed out and replaced. However, if the mechanic finds the fluid to be excessively contaminated, then the transmission has likely been seriously damaged, and a rebuild or replacement is likely.
• Next, visually inspect the electrical components. Any damaged wires, connectors, or blown fuses will require replacement. If any of these components appear to have been damaged by leaks, or other reasons outside of basic wear and tear, then a further inspection will be required. The mechanic should then check the output speed sensors by checking their ground signal and reference voltage.
• After any issue is identified and replaced, reset the trouble codes and restart the vehicle, to check again for the P0738 code. This helps the technician know as soon as the problem has been resolved.

Common Mistakes When Diagnosing the P0738 Code

• Check for Crankshaft Position Sensor failure
• Powertrain Control Module (PCM) failure that may require reprogramming or replacement
• Transmission Control Module (TCM) failure that might need replacement
• Wiring and connector issue