P00FD: Battery B State of Charge Performance

'Battery B' here is not a hybrid high-voltage battery (those have codes from P0B27) but, in the only documented use by FCA/Stellantis, the 12 V auxiliary battery of the start-stop system. When the engine restarts automatically, a relay separates main and auxiliary battery so that the auxiliary one keeps the control units stable while the main battery cranks. The engine module sets P00FD if the auxiliary battery is disconnected on the first start, drops below about 8 V during an auto-start, or repeatedly falls below 10.3 V (counter reaches ten). Start-stop is then disabled; often it follows a jump start or many short trips. Whether the MIL comes on is not stated in the sources.

Medium severity. Can I keep driving?If the battery warning light comes on, you could get stranded. Turn off electrical accessories and go straight to a repair shop.

Symptoms

Start-stop out of service, 'Service Start/Stop' message
Engine does not crank once
'Service Shifter' message with electronic gear selector

Most likely causes

Auxiliary battery discharged or aged
Loose or corroded positive or ground connections at either battery
150 A fuse or fuse array in the power distribution centre open or poorly contacting
Battery separation relay stuck
Main battery faulty

What to check, in order

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

Measure the voltage with the engine off and running
Compare the reading with other engine data while varying the engine speed.
Clean and tighten the terminals
Check the accessory belt
Run a battery load test
Check the alternator wiring

Good to know

Repair difficulty: easy

What each character of P00FD means

P: Powertrain: engine and transmission
0: Generic code: same on every make
0: Subsystem depends on the code range
FD: Specific fault in that system

Frequently asked questions

Can I keep driving with code P00FD?

If the battery warning light comes on, you could get stranded. Turn off electrical accessories and go straight to a repair shop.

What causes code P00FD?

The most common causes are: auxiliary battery discharged or aged; loose or corroded positive or ground connections at either battery; 150 A fuse or fuse array in the power distribution centre open or poorly contacting.

Related codes

Sources

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.