Fix P0738: STEP-BY-STEP diagnostic GUIDE!

The P0738: TCM Engine Speed Output Circuit Low refers to a condition where the transmission control module (TCM) detects a low signal from the engine speed output circuit. This could result from wiring issues, faulty components, or electrical problems in the circuit.

P0738 – Quick Overview

CodeInformation
MeaningP0738: TCM Engine Speed Output Circuit Low
Is it serious?Yes, this can affect communication between the engine and TCM, leading to improper transmission performance.
Possible causes– Low signal from TCM engine speed output circuit
– Faulty circuit or components
– Wiring issues
How to diagnose?– Test the circuit for low signal
– Inspect wiring and connectors
– Replace faulty components if necessary

P0738 Meaning

The P0738 code indicates that the transmission control module (TCM) is receiving a low signal from the engine speed output circuit. This could be due to a malfunction in the circuit, damaged wiring, or issues with the connectors, leading to poor communication between the engine and the TCM, which can affect the transmission’s performance.

Step-by-step diagnostic guide

ActionDescriptionTools Needed
Check for Other CodesUse an OBD-II scanner to detect if there are additional codes related to the TCM or engine speed that might help diagnose the problem.OBD-II Scanner
Test the Circuit for Low SignalUse a multimeter or diagnostic scanner to measure the signal strength from the TCM engine speed output circuit and confirm if it is below specifications.Multimeter, Diagnostic Scanner
Inspect Wiring and ConnectorsInspect the wiring and connectors between the engine speed sensors and TCM for damage, wear, or loose connections that could cause signal loss.Flashlight, Multimeter, Safety Gloves
Check for Electrical FaultsTest for any electrical faults, such as short circuits or open circuits, that may be causing the low signal from the TCM engine speed output.Circuit Tester, Multimeter
Replace Faulty ComponentsReplace any defective wiring, connectors, or TCM components that are contributing to the low signal in the circuit.Replacement Parts, Wrenches, Screwdrivers
Clear the Code and Test DriveAfter making repairs, clear the code with an OBD-II scanner and test drive the vehicle to verify that the issue is resolved.OBD-II Scanner
Recheck for CodesAfter the test drive, rescan the vehicle to ensure that the P0738 code has not returned.OBD-II Scanner
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