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
Code | Information |
---|---|
Meaning | P0738: 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
Action | Description | Tools Needed |
---|---|---|
Check for Other Codes | Use 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 Signal | Use 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 Connectors | Inspect 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 Faults | Test 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 Components | Replace 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 Drive | After 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 Codes | After the test drive, rescan the vehicle to ensure that the P0738 code has not returned. | OBD-II Scanner |

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