P0738Generic code

P0738 Code: TCM Engine Speed Output Circuit Low

The P0738 code means the engine speed signal that the transmission computer sends to other components, such as the tachometer or other modules, is reading low. The transmission usually keeps working normally. The most common result is a dead tachometer.

Severity
Low
Can I keep driving?
Yes, no immediate risk
Estimated cost
$0 to $300
Difficulty
Medium
System
Transmission
Applies to
All OBD2 vehicles

Updated Reviewed by Renzo Chacca

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What the P0738 code means

On some vehicles the transmission computer relays the engine speed signal to other components, such as the tachometer. If that output circuit is shorted or open and the signal reads low, the computer stores the P0738 code.

The tachometer may stop working, while the transmission usually keeps shifting as normal.

If the tachometer quit after an accessory was installed (an alarm, a remote starter or an add-on tachometer), unplug that accessory and see whether the code goes away. It is the most common cause of these output codes.

P0738 code symptoms

  • Tachometer that does not work.
  • Check engine light on.

Likely causes of the P0738 code

  1. Output circuit shorted or open between the computer and the receivers.
  2. Instrument cluster or receiving module that loads down the signal.
  3. Loose or corroded connector.

How to diagnose the P0738 code step by step

  1. Measure the signal at the output.
  2. Unplug the receivers and check whether the code goes away.

How to fix the P0738 code

  • Repair the wiring or the receiving device.

Technical reference data

  • Pulse signal.
  • Reference values: check the manufacturer data for your vehicle.

Brand-specific notes

This code shows up on some Chrysler and Ford vehicles.

P0738 on Chrysler

It appears on some Chrysler vehicles. Check the manufacturer data for your model.

P0738 on Ford

It also appears on some Ford vehicles. Check the manufacturer data for your model.

Frequently asked questions about P0738

Can I drive with a P0738 code?
Yes. A P0738 code is low severity and the vehicle is normally safe to drive, though a dead tachometer is a nuisance.
Does it affect the transmission?
Normally it does not. The fault is in the signal sent out to other devices, not in how the transmission shifts.
What stops working because of it?
Usually the tachometer or other modules that depend on the engine speed signal.
How much does it cost to fix P0738?
It runs from $0 to $300. Reconnecting a connector costs nothing, while a wiring repair or a receiving module costs more.
What does the P0738 code mean?
It is a generic OBD2 code for a low signal in the transmission computer engine speed output circuit. The signal it relays to the tachometer and other modules is shorted or open.

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Questions about the P0738 code

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