A failed excitation current sensor that internally shorts its signal line to ground; A chafed or pinched signal wire in the sensor harness rubbing against a grounded metal surface; Corrosion or water intrusion at the sensor connector causing a low-resistance path to ground; A poor ground connection for the sensor or the motor assembly that skews the voltage reference; An internal fault in the drive motor A assembly, such as a shorted field winding or damaged exciter circuit; A faulty powertrain control module with a damaged internal pull-up resistor or analog input circuit

DTC codes / P2Exx · Hybrid propulsion / P2E29

P2E29Drive Motor A Excitation Current Sensor Circuit Low Voltage

Q: What does code P2E29 mean?

Drive Motor A Excitation Current Sensor Circuit Low Voltage. P2E29 indicates that the powertrain control module has detected an abnormally low voltage signal from the excitation current sensor circuit of drive motor A, which is the sensor that monitors the field or excitation current supplied to the motor's rotor or field winding. The computer expects the sensor's output voltage to stay within a calibrated range, and a sustained low reading tells the module that the circuit is shorted to ground, the sensor has failed, or the motor's excitation current is genuinely too low.

P2E29 indicates that the powertrain control module has detected an abnormally low voltage signal from the excitation current sensor circuit of drive motor A, which is the sensor that monitors the field or excitation current supplied to the motor's rotor or field winding. The computer expects the sensor's output voltage to stay within a calibrated range, and a sustained low reading tells the module that the circuit is shorted to ground, the sensor has failed, or the motor's excitation current is genuinely too low.

SystemPowertrain

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyProfessional

AreaHybrid propulsion

Symptoms you may notice

Illumination of the check engine light or service vehicle soon message, often with no other noticeable symptoms
Reduced power or a limp-home mode that limits motor output to protect the drive system
Intermittent hesitation or a sudden loss of propulsion assist during acceleration
A stored code accompanied by a freeze-frame showing low sensor voltage at the time of the fault
In rare cases, a burning smell or visible damage at the sensor connector if the short is internal to the harness
No driver-perceptible change in vehicle behavior besides the warning light in many cases

Common causes, most likely first

A failed excitation current sensor that internally shorts its signal line to ground
A chafed or pinched signal wire in the sensor harness rubbing against a grounded metal surface
Corrosion or water intrusion at the sensor connector causing a low-resistance path to ground
A poor ground connection for the sensor or the motor assembly that skews the voltage reference
An internal fault in the drive motor A assembly, such as a shorted field winding or damaged exciter circuit
A faulty powertrain control module with a damaged internal pull-up resistor or analog input circuit

How to diagnose and fix it

Connect a scan tool and record the freeze-frame data for P2E29, then clear the code and verify whether it returns immediately or only under specific load conditions
Visually inspect the excitation current sensor connector and the full length of its harness for chafing, corrosion, moisture, or loose pins
Measure the sensor's reference voltage and ground at the connector with a digital multimeter and compare against the manufacturer's specification
Back-probe the signal wire and check for a short to ground with the sensor disconnected, then wiggle the harness to reveal intermittent faults
Test the excitation current sensor with a known-good substitute or perform a resistance and voltage output check per the service information
If the circuit and sensor test good, inspect the drive motor A field winding and exciter circuit for an internal short or low resistance
As a final step, verify the powertrain control module's analog input by checking for a shorted internal circuit or replacing the module only after all other causes are ruled out

When the sensor is not the real culprit

A low voltage reading on this circuit is frequently caused by a shorted signal wire where the harness passes near a sharp bracket or a heat source, not by a failed sensor, so a thorough wiggle test with a multimeter connected is essential before replacing parts.
Water intrusion into the sensor connector is a common missed cause on vehicles that have been driven through deep puddles or have a clogged underbody drain, and the corrosion often hides inside the terminal cavity.
Technicians sometimes replace the excitation current sensor only to find the code returns because the motor's field winding has an internal short that pulls the excitation current down, which the sensor faithfully reports as a low voltage.
A poor chassis ground for the motor or the sensor can elevate the ground reference and make a normal sensor signal appear low to the control module, so ground voltage drop testing should always accompany sensor testing.
This code can set intermittently from a momentary harness rub that only occurs during certain suspension movements, so a single clear-and-drive test may not reproduce the fault and a road test over rough surfaces may be needed.

Can I keep driving with P2E29?

The vehicle may enter a reduced-power mode, which can make merging or climbing hills difficult, so limit driving to low-speed routes until the fault is repaired. Avoid heavy acceleration or sustained high-load operation, and if the warning light begins flashing or the vehicle loses propulsion entirely, stop driving and arrange a tow.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.