What Does P1309 Mean?
P1309 indicates the chassis acceleration sensor signal is above the expected voltage range. The PCM detects an abnormally high voltage on the sensor output, suggesting a short to the reference voltage or power supply. This disables the rough road misfire compensation, potentially causing false or missed misfire detections.
Common Causes
30%
Short to voltage in the sensor signal wire
30%
Failed chassis acceleration sensor (output stuck high)
20%
Open circuit in the sensor ground wire
15%
Connector terminal damage causing signal-to-power short
5%
PCM internal pull-up failure on input circuit
Diagnostic Steps
1
Inspect the chassis acceleration sensor connector for bent pins, spread terminals, or contamination that could cause cross-connection.
2
Disconnect the sensor and measure signal wire voltage — if it drops to near zero, the sensor is shorted internally.
3
Check for a short between the signal wire and the 5V reference wire by measuring resistance between them with both ends disconnected.
4
Verify the sensor ground wire has continuity back to the PCM and is not open.
5
Monitor the sensor PID after repairs to confirm the signal stays within the normal operating range.
Estimated Repair Cost
$80 - $350
Parts + labor, varies by vehicle and location
P1309 indicates the chassis acceleration sensor signal is above the expected voltage range. The PCM detects an abnormally high voltage on the sensor output, suggesting a short to the reference voltage or power supply. This disables the rough road misfire compensation, potentially causing false or mi...
The most common cause of P1309 (Chassis Acceleration Sensor Signal High) is: Short to voltage in the sensor signal wire
Typical repair costs for P1309 range from $80 to $350, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Without valid chassis acceleration data, the PCM may incorrectly attribute rough road vibrations as misfires or miss actual misfires. This indirectly affects emissions and catalyst protection but poses no immediate driving hazard.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P1309 to identify the root cause.
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Quick Info
Category
Powertrain
System
Engine Management / Misfire Detection
Difficulty
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