What Does P1129 Mean?
This code sets when the throttle position sensor (TPS) output voltage falls outside the expected range during the ECM's self-test procedure. The ECM checks TPS voltage at specific throttle openings and if the reading is too high, too low, or erratic, this code is triggered. This can indicate a misadjusted, worn, or faulty TPS, or issues with the throttle body itself.
Common Causes
30%
Throttle position sensor out of adjustment or calibration
25%
Worn or faulty throttle position sensor
20%
Dirty or carbon-fouled throttle body preventing proper blade movement
15%
Damaged TPS wiring or connector with intermittent contact
10%
Throttle body mechanical binding or sticking
Diagnostic Steps
1
Monitor TPS voltage live data at closed throttle (should be approximately 0.5-0.9V) and wide open throttle (should be approximately 4.0-4.5V).
2
Slowly sweep the throttle from closed to wide open while watching for voltage dropouts, dead spots, or erratic readings.
3
Inspect the TPS connector for corroded, bent, or backed-out pins and verify a solid connection.
4
Clean the throttle body thoroughly and verify the throttle blade moves freely without binding.
5
If the TPS is adjustable, verify proper alignment and re-learn the throttle position with a scan tool if applicable.
6
Replace the TPS if voltage readings are erratic or out of specification.
Estimated Repair Cost
$50 - $250
Parts + labor, varies by vehicle and location
This code sets when the throttle position sensor (TPS) output voltage falls outside the expected range during the ECM's self-test procedure. The ECM checks TPS voltage at specific throttle openings and if the reading is too high, too low, or erratic, this code is triggered. This can indicate a misad...
The most common cause of P1129 (Throttle Position Sensor Out Of Self Test Range) is: Throttle position sensor out of adjustment or calibration
Typical repair costs for P1129 range from $50 to $250, depending on the vehicle, location, and whether you do it yourself or go to a shop.
A faulty TPS can cause erratic idle, hesitation on acceleration, and unpredictable throttle response. On drive-by-wire systems, this may trigger a reduced power or limp mode for safety.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P1129 to identify the root cause.
OBDHut Mobile App
Scan codes directly from your car with the OBDHut app.
Coming Soon
Quick Info
Category
Powertrain
System
Electronic Throttle Control
Difficulty
Type
Manufacturer
Recommended Tools
OBD2 Scanner
A quality scan tool helps you read codes, view live data, and clear faults.
