P0ADF: Hybrid/EV Battery Negative Contactor Control Circuit Low

P0ADF reports that the drive circuit of the negative main contactor is pulled too low, typically a short to ground in the coil line. GM documents the code in its 2016-19 hybrid tables: control voltage below 5.35 V while the contactor is commanded on, 13 of 16 samples at 12.5 ms (20 of 25 in one 2016 group), Type B with two trips, enabled above about 9 to 10 V on the 12 V system. CARB 1968.2 requires this kind of circuit monitoring for hybrid outputs. Counterparts are P0ADD (open), P0AE0 (high) and, on the positive side, P0ADB. As the contactor cannot close properly, the high-voltage system does not come up and the vehicle will not drive or charge.

Symptoms

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

Most likely causes

• Coil control wire shorted to ground
• Negative contactor coil internally shorted
• Moisture in the battery disconnect unit connector
• 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. With the connector unplugged, check whether the signal wire is making contact with ground.
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 P0ADF means

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

Frequently asked questions

Can I keep driving with code P0ADF?

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 P0ADF?

The most common causes are: coil control wire shorted to ground; negative contactor coil internally shorted; moisture in the battery disconnect unit connector.

Related codes

• P0ADDHybrid/EV Battery Negative Contactor Control Circuit/Open
• P0ADEHybrid/EV Battery Negative Contactor Control Circuit Range/Performance
• P0AE0Hybrid/EV Battery Negative Contactor Control Circuit High
• P0ADBHybrid/EV Battery Positive Contactor Control Circuit Low

Sources

• gsi.ext.gm.com: 16OBDG02 Hybrid Diagnostics
• law.cornell.edu: 13 CCR 1968.2
• gsi.ext.gm.com: 16OBDG07B Engine 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.