P0AD9: Hybrid/EV Battery Positive Contactor Control Circuit/Open

The positive main contactor connects the traction battery to the high-voltage bus; its coil is driven by the battery or hybrid controller. P0AD9 covers an open in this coil circuit. GM documents it in detail: in hybrid tables from model year 2011 the HPC2 sets it on open load during the commanded state, Type B. 2016-19 tables use a control voltage between 1.15 and 2.81 V with the contactor commanded off, 40 of 50 samples at 12.5 ms; 2019 versions also check coil current below 194 mA when on. CARB requires circuit monitoring of hybrid outputs. Low and high faults are P0ADB and P0ADC; a contactor stuck open is P0AA2. The car usually cannot go ready.

Symptoms

• Vehicle will not enter ready mode or start
• Hybrid or EV warning light and check engine light
• Charging not possible

Most likely causes

• Open in the contactor coil or its pigtail inside the battery disconnect unit
• Loose or corroded low-voltage connector at the battery disconnect unit
• Broken control wire in the battery harness
• High-side driver in the battery controller defective

What to check, in order

Start with the simplest. You can tick off each step.

1. Read the codes with a hybrid-compatible scanner and write down the freeze frame data
2. Check the continuity of the wire between the component and the control module.
3. Make sure the battery cooling air intake is clean
4. Check the 12 V auxiliary battery, which can also trigger warnings
5. Leave any high-voltage measurements to a specialized repair shop

Good to know

• It can trigger limp mode.
• It affects emissions.

What each character of P0AD9 means

• P: Powertrain: engine and transmission
• 0: Generic code: same on every make
• A: Hybrid or air and fuel
• D9: Specific fault in that system

Frequently asked questions

Can I keep driving with code P0AD9?

If the car still runs, drive as little as possible and go to a specialized repair shop. Do not touch the orange cables: they carry high voltage.

What causes code P0AD9?

The most common causes are: open in the contactor coil or its pigtail inside the battery disconnect unit; loose or corroded low-voltage connector at the battery disconnect unit; broken control wire in the battery harness.

Related codes

• P0ADAHybrid/EV Battery Positive Contactor Control Circuit Range/Performance
• P0ADBHybrid/EV Battery Positive Contactor Control Circuit Low
• P0ADCHybrid/EV Battery Positive Contactor Control Circuit High
• P0ADDHybrid/EV Battery Negative Contactor Control Circuit/Open
• P0AA2Hybrid/EV Battery Positive Contactor Circuit Stuck Open
• P0AE4Hybrid/EV Battery Precharge Contactor A Control Circuit/Open

Sources

• law.cornell.edu: 13 CCR 1968.2
• gsi.ext.gm.com: 16OBDG02 Hybrid Diagnostics
• gsi.ext.gm.com: 19OBDG01 Hybrid Diagnostics

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.