What Does P1124 Mean?
P1124 indicates the Throttle Position Sensor signal fell outside the acceptable range during the ECM's self-test procedure. During key-on engine-off or key-on engine-running self-tests, the ECM checks that the TPS voltage is within a predefined window. A signal outside this window suggests the TPS is miscalibrated, the throttle is not in its expected rest position, or there is a circuit fault affecting the signal.
Common Causes
30%
TPS base voltage out of specification at closed throttle
25%
Throttle plate not returning to the fully closed position (sticking)
18%
TPS connector pins corroded or making intermittent contact during self-test
15%
Idle air control system malfunction affecting throttle position at rest
12%
TPS sensor internally worn and output drifted from original calibration
Diagnostic Steps
1
Step 1: With key on engine off, read TPS voltage. Verify it falls within the self-test window specified by the manufacturer (typically 0.4–1.0V closed, 4.0–4.5V wide open).
2
Step 2: Manually move the throttle from closed to wide open while monitoring voltage. The signal should increase smoothly and linearly with no jumps, dead spots, or dropout.
3
Step 3: Ensure the throttle plate is fully closed when released. Inspect for binding, carbon deposits, or a stiff return spring that prevents complete closure.
4
Step 4: Check the idle air control valve or electronic idle actuator. If it is commanding the throttle slightly open during the self-test, the TPS reading will be out of range.
5
Step 5: Adjust the TPS (if adjustable) to bring the closed-throttle voltage within specification. For non-adjustable TPS, replace the sensor or throttle body assembly.
6
Step 6: Clear codes and re-run the self-test (KOEO and KOER) using the scan tool to verify the TPS passes both test conditions.
Estimated Repair Cost
$40 - $350
Parts + labor, varies by vehicle and location
P1124 indicates the Throttle Position Sensor signal fell outside the acceptable range during the ECM's self-test procedure. During key-on engine-off or key-on engine-running self-tests, the ECM checks that the TPS voltage is within a predefined window. A signal outside this window suggests the TPS i...
The most common cause of P1124 (Throttle Position Sensor Signal Out of Self Test Range) is: TPS base voltage out of specification at closed throttle
Typical repair costs for P1124 range from $40 to $350, depending on the vehicle, location, and whether you do it yourself or go to a shop.
An out-of-range TPS signal during self-test may trigger failsafe mode on the next drive cycle, limiting throttle response and engine power. This could be hazardous if it occurs unexpectedly in high-speed traffic.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P1124 to identify the root cause.
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Quick Info
Category
Powertrain
System
Engine Management / Throttle Control
Difficulty
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