P1128
System
Powertrain (Throttle)
Scanner required
Enhanced OBD2 scanner (live data graphs, freeze frame, battery voltage test)

Throttle Control Motor Circuit Low (GM)

Understand P1128, common causes, and the right SEAFLO pump to diagnose it.

GM throttle actuator motor circuit shorted low — common after throttle body cleaning if connector not seated.

Common symptoms

  • Engine power reduced
  • Pedal dead zone
  • Idle surge

Typical causes

  • Short in TAC motor circuit
  • Failed throttle body
  • Water intrusion in connector

What scanner do you need?

Enhanced OBD2 scanner (live data graphs, freeze frame, battery voltage test)

Use live data and freeze frame to confirm the fault before replacing parts. ABS, SRS, and network U-codes usually require a full-system scanner.

Diagnostic tips

  • Record freeze frame data when the code first sets
  • Clear the code only after fixing the root cause
  • Check for related pending codes that point to a common issue
  • Verify battery voltage is above 12.4V before chasing sensor codes

Frequently asked questions

Can I diagnose P1128 with a basic code reader?
P1128 may set in the engine module, but related diagnostics often benefit from an enhanced or full-system scanner with live data and freeze frame.
Is it safe to drive with P1128?
It depends on the code and symptoms. Flashing check engine lights and misfire codes should be addressed immediately. Consult a professional if unsure.