What Does P1224 Mean?
P1224 indicates that the Throttle Position Sensor B (TPS-B) signal was out of the expected self-test range during an ECM key-on engine-off (KOEO) or key-on engine-running (KOER) self-test. The ECM uses the secondary TPS as a redundancy check, and if its output does not fall within the expected voltage window at closed throttle or during the test sweep, this code is stored.
Common Causes
30%
Faulty or drifted Throttle Position Sensor B
20%
Carbon deposits on the throttle blade preventing full closure during self-test
20%
Corroded or loose connector at the throttle body TPS connector
15%
Damaged wiring between the TPS-B and the ECM
15%
Throttle body mechanical binding or misadjustment
Diagnostic Steps
1
Perform a KOEO self-test and monitor TPS-B voltage at closed throttle. Compare to manufacturer specification (typically 0.5-1.0V at closed throttle for sensor B, depending on application).
2
Monitor TPS-B signal while slowly opening the throttle from closed to wide-open. The voltage should increase smoothly and linearly with no dead spots or jumps.
3
Compare TPS-A and TPS-B signals simultaneously. They should track proportionally (often inversely). Discrepancies indicate a failing sensor.
4
Inspect the throttle body for carbon buildup that prevents the blade from fully closing. Clean with approved throttle body cleaner if needed.
5
Check the TPS connector for corrosion, moisture, and proper terminal engagement. Verify the 5V reference and ground circuits are within specification.
6
If the sensor is integrated into the throttle body, replace the throttle body assembly and perform a throttle position relearn procedure.
Estimated Repair Cost
$150 - $600
Parts + labor, varies by vehicle and location
P1224 indicates that the Throttle Position Sensor B (TPS-B) signal was out of the expected self-test range during an ECM key-on engine-off (KOEO) or key-on engine-running (KOER) self-test. The ECM uses the secondary TPS as a redundancy check, and if its output does not fall within the expected volta...
The most common cause of P1224 (Throttle Position Sensor B Out Of Self Test Range) is: Faulty or drifted Throttle Position Sensor B
Typical repair costs for P1224 range from $150 to $600, depending on the vehicle, location, and whether you do it yourself or go to a shop.
An out-of-range TPS-B can cause the ECM to enter reduced power mode as a precaution, limiting vehicle speed and throttle response. If both TPS sensors fail or show conflicting data, the throttle control system may shut down entirely, creating a potentially dangerous loss of power.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P1224 to identify the root cause.
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Quick Info
Category
Powertrain
System
Electronic Throttle Control System
Difficulty
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