P0D18

What it means

P0D18 means the control unit monitoring the high voltage interlock loop for battery charging system A has measured a circuit voltage higher than expected. The interlock is a low-voltage safety loop that confirms charging-related high voltage connectors, covers and components are secure before high voltage is allowed. A high reading usually points to a short to voltage or a fault in the loop. Exactly how the loop is wired and what counts as 'high' depends on the make and model.

Symptoms

• Hybrid or EV system warning light or charging fault message on the dash
• Vehicle will not charge from the charge port or from the on-board charger
• High voltage system may not enable, or the car may not go to 'ready'
• Reduced power or limp mode on some models
• Charge port lock or charging indicator behaving oddly

Possible causes

• Damaged, corroded or contaminated terminals or connectors in the interlock loop at the charger, charge port or high voltage batterylikely
• Interlock wiring short to a voltage supply, or chafed or pinched harnesslikely
• Faulty or incorrectly seated interlock switch or connector on the on-board charger, charge inlet or related high voltage componentpossible
• Water ingress in the charge port, charger or connector housingspossible
• Fault inside the charger control module or the module that monitors the interlockpossible
• Outdated or faulty control unit software, only where the manufacturer lists it as a known cause for this modelrare

How to diagnose

1. Only trained, suitably qualified staff should work on high voltage systems. Follow the manufacturer's high voltage isolation and safety procedure before touching any orange cable or connector.
2. Read all stored and pending codes and the freeze frame data, noting whether the fault is current or intermittent and whether other charging or interlock codes are present.
3. Visually inspect the charge port, charger and high voltage connectors for damage, moisture, corrosion, bent pins or covers not fitted correctly.
4. Check that all high voltage connectors and covers in the charging circuit are fully seated and their locking mechanisms are engaged.
5. Inspect the low-voltage interlock harness for chafing, pinching, previous repair damage or signs of a short to a power feed.
6. With the system isolated, test the interlock loop for shorts to voltage and for resistance against the manufacturer's specification for that model.
7. Check the interlock switches or bridging terminals for correct operation and contact resistance.
8. If wiring and connectors are sound, check for a published software update or service bulletin before suspecting the control module.

How to fix

• Clean, dry out or replace corroded or contaminated connectors and terminals, and refit any seals
• Repair or replace damaged interlock wiring that is shorted to voltage
• Refit and secure any loose high voltage connector or cover so the interlock closes correctly
• Replace a faulty interlock switch, charge inlet or charger component confirmed by testing
• Update the control unit software only if the manufacturer lists it as a known fix for this code, or replace a confirmed faulty module

Can I keep driving?

Nearby codes

• P0D17GenericBattery Charging System A High Voltage Interlock Circuit Low
• P0D19GenericBattery Charging System A High Voltage Interlock Circuit Intermittent/Erratic