Faulty precharge contactor A itself, such as worn contacts or a stuck armature; Damaged or corroded wiring or connectors in the precharge contactor control circuit; A failed precharge resistor that alters the expected current profile during precharge; Poor ground connection for the contactor coil or control module; Malfunctioning battery management system or control module driver for the contactor; Low 12-volt auxiliary battery voltage causing erratic contactor operation

DTC codes / P0Axx · Hybrid propulsion / P0AE5

P0AE5Hybrid/EV Battery Precharge Contactor A Control Circuit Range/Performance

P0AE5 indicates that the hybrid or electric vehicle's battery management system has detected an out-of-range or performance fault in the control circuit for the precharge contactor A, which is the relay that safely connects the high-voltage battery to the rest of the vehicle's electrical system through a resistor before the main contactor closes. The computer monitors the circuit for expected voltage and current behavior and sets this code when the signals do not match the commanded state.

SystemPowertrain

Code typeGeneric (all makes)

SeverityHigh

Fix difficultyProfessional

AreaHybrid propulsion

Symptoms you may notice

Illumination of the hybrid system warning light or master warning indicator
The vehicle may refuse to start or enter 'Ready' mode, leaving you with a no-start condition
A message on the dash such as 'Hybrid System Failure' or 'Check Hybrid System'
Possible reduction in power or limited driving speed if the vehicle does enter ready mode
Often no symptoms besides the warning light, especially if the fault is intermittent

Common causes, most likely first

Faulty precharge contactor A itself, such as worn contacts or a stuck armature
Damaged or corroded wiring or connectors in the precharge contactor control circuit
A failed precharge resistor that alters the expected current profile during precharge
Poor ground connection for the contactor coil or control module
Malfunctioning battery management system or control module driver for the contactor
Low 12-volt auxiliary battery voltage causing erratic contactor operation

How to diagnose and fix it

Perform a thorough visual inspection of the precharge contactor, its connectors, and the wiring harness for damage, corrosion, or loose pins
Check the 12-volt auxiliary battery state of charge and condition, as low voltage can cause false contactor codes
Measure the resistance of the precharge contactor coil and compare to specifications, and check for continuity through the control circuit
Use a scan tool to command the precharge contactor on and off while monitoring the control circuit voltage and current to verify operation
Inspect the precharge resistor for signs of overheating or open circuit, and replace if out of specification
If the circuit and resistor are good, test the contactor by applying power directly to the coil and listening for a click, then check for continuity across the power terminals when closed
Replace the precharge contactor assembly if it fails electrical or mechanical testing, and clear the code to verify the repair

What the precharge contactor code hides

A weak or failing 12-volt battery is a common culprit behind this code because the contactor coil needs a solid voltage supply to pull in reliably, and a sagging battery can cause intermittent performance faults.
The precharge contactor works with a resistor to limit inrush current, so a fault in the resistor or its connections can set this code even when the contactor itself is fine.
Technicians sometimes replace the contactor only to find the real problem is a chafed wire in the control circuit, so always perform a voltage drop test on both the power and ground sides of the coil.
This code can be set by a momentary glitch during a low-voltage event, so after repairs, clear the code and drive the vehicle through several key cycles to confirm it does not return.
On some vehicles, the precharge contactor is part of a non-serviceable assembly, and the entire high-voltage battery junction box must be replaced, so check service information before ordering parts.

Can I keep driving with P0AE5?

Do not continue driving with this code active, as a faulty precharge contactor can prevent the high-voltage system from energizing safely or cause a sudden loss of power. Have the vehicle inspected by a qualified hybrid technician before attempting to drive further.

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.