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P0738 OBD2: TCM Engine Speed Output Circuit Low

P0738 OBD2: TCM Engine Speed Output Circuit Low

What Does the P0738 Code Mean?

OBD-II Code P0738 is defined as a TCM Engine Speed Output Circuit Low. This code indicates that the Transmission Control Module is receiving an inaccurate signal regarding the engine’s speed, preventing it from executing proper gear shifts.

What Causes the P0738 Code?

The P0738 code can be triggered by several factors, including:

  • Crankshaft Position Sensor (CKP) failure
  • Powertrain Control Module (PCM) failure
  • Transmission Control Module (TCM) failure
  • Wiring issues related to the engine speed sensor

What Are the Symptoms of the P0738 Code?

Drivers may notice the following symptoms when the P0738 code is present:

  • Increased fuel consumption
  • Transmission may not shift properly

How Serious Is the P0738 Code?

While the P0738 code is categorized as moderate severity, it is essential to address it promptly. Ignoring this issue could lead to more severe problems with the transmission and overall vehicle performance.

How to Diagnose the P0738 Code

Diagnosing the P0738 code requires a systematic approach:

  1. Use an OBD-II scanner to confirm the presence of the P0738 code.
  2. Inspect the Crankshaft Position Sensor and its wiring for damage or disconnection.
  3. Check the Transmission Control Module for faults.
  4. Evaluate the Powertrain Control Module for any issues.

Common Repairs for the P0738 Code

To resolve the P0738 code, you may need to perform one or more of the following repairs:

  • Replace the Crankshaft Position Sensor
  • Repair or replace faulty wiring
  • Replace the Transmission Control Module
  • Replace the Powertrain Control Module if necessary

How Much Does It Cost to Fix the P0738 Code?

The cost of repairs associated with the P0738 code can vary significantly based on the underlying issue. Typical expenses may range from $100 to $1,500, depending on whether you need to replace sensors, modules, or wiring.

Can I Fix the P0738 Code Myself?

While some DIY enthusiasts may attempt to fix the P0738 code, it is generally recommended to consult a professional mechanic. Diagnosing and repairing transmission-related issues can be complex and requires specific tools and expertise.

About JC Landry

JC is the Senior Editor at eManualOnline.com, GarageSpot.com, and Drive-My.com, as well as the Webmaster of TheMechanicDoctor.com, only to name a few. He's been a certified Master Mechanic for 15 years, working for various car dealers and specialized repair shops before turning towards blogging about cars and EVs in the hope of helping the next generation of automotive technicians. He also loves cats, Johnny Cash and Subarus.

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