What Does P0A42 Mean?
DTC P0A42 indicates the drive motor "A" position sensor circuit output is above the maximum expected signal level. In a resolver-based system, this typically means the resolver output signals exceed the normal amplitude range, which can occur due to a short circuit in the sensor or wiring, an incorrect excitation voltage, or electromagnetic interference coupling into the signal wires. The abnormally high signal level corrupts the position data, preventing the Hybrid Control Module from accurately determining the rotor angle for motor commutation. The HCM will typically disable motor "A" operation to prevent commutation errors.
Safety Warning
An abnormally high position sensor signal can cause severe motor commutation errors, potentially resulting in unpredictable torque spikes, motor vibration, or immediate motor shutdown. This can cause abrupt changes in vehicle drive force.
Common Causes
30%
Short circuit between resolver signal wires or to the excitation supply
25%
Electromagnetic interference coupling into the position sensor wiring from motor phase cables
20%
Damaged wiring harness with compromised shielding allowing noise pickup
15%
Inverter resolver excitation circuit producing excessive voltage
10%
Internal sensor fault causing abnormally high output
Diagnostic Steps
1
Step 1: Check the motor "A" position sensor live data. An out-of-range or oscillating position value suggests signal corruption from a high circuit condition.
2
Step 2: Disconnect the position sensor and check for shorts between all signal wires, excitation wires, and ground at the sensor connector and along the harness.
3
Step 3: Inspect the resolver wiring harness routing and shielding. Ensure the signal wires are properly shielded and routed separately from the high-current motor phase cables.
4
Step 4: With the sensor connected, use an oscilloscope to measure the resolver output signal amplitudes and look for noise or distortion superimposed on the expected sinusoidal signals.
5
Step 5: Measure the excitation voltage at the sensor to verify it is within specification. An overvoltage condition from the inverter excitation circuit would cause high output signals.
Estimated Repair Cost
$350 - $2,200
Parts + labor, varies by vehicle and location
DTC P0A42 indicates the drive motor "A" position sensor circuit output is above the maximum expected signal level. In a resolver-based system, this typically means the resolver output signals exceed the normal amplitude range, which can occur due to a short circuit in the sensor or wiring, an incorr...
The most common cause of P0A42 (Drive Motor "A" Position Sensor Circuit High) is: Short circuit between resolver signal wires or to the excitation supply
Typical repair costs for P0A42 range from $350 to $2,200, depending on the vehicle, location, and whether you do it yourself or go to a shop.
An abnormally high position sensor signal can cause severe motor commutation errors, potentially resulting in unpredictable torque spikes, motor vibration, or immediate motor shutdown. This can cause abrupt changes in vehicle drive force.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P0A42 to identify the root cause.
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Quick Info
Category
Powertrain
System
Hybrid/EV Drivetrain
Difficulty
Type
Generic (SAE)
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