P0738
PowertrainTransmissionmoderate severityTCM Engine Speed Output Circuit Low
What P0738 Means
The engine speed output circuit from the transmission control module reads low. A low signal on this circuit can disrupt speed-based control functions.
Symptoms
- Shifting irregularities
- Check engine light on
- Speed signal complaints
Common Causes
- Short to ground in circuit
- Corroded connector
- Wiring damage
- Faulty TCM
Diagnostic Steps
- Retrieve codes and freeze frame
- Inspect circuit for short to ground
- Measure output circuit voltage
- Repair wiring or replace TCM
🔌 Don't have a code reader?
Any of these will read and clear this code — pick by how deep you want to go.
Budget handheld~$40
ANCEL AD410 →
No-phone-needed handheld — reads, clears, live data, freeze frame.
✓ ANCEL official store
Serious DIY~$100
BlueDriver Pro →
Enhanced codes (ABS, airbag, TPMS) plus repair reports.
SHOP FAVORITEShop-grade tablet~$300
Autel MaxiCOM MK808S →
Bidirectional tests, service resets, all systems.
✓ Autel official store
Pro diagnostics$1,500+
Autel MaxiSys MS906 Pro →
Full-system pro platform — topology mapping, ECU coding, the works.
✓ Autel official store
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