What it means
The charge sequence signal 1 circuit of battery charger B reports voltage above the expected window. Charging handshake compromised.
At a glance
- Usually lights the check-engine light
- The engine or gearbox may go into limp mode
How it works
Battery charger B uses charge-sequence signal 1 as part of its charging handshake with the vehicle. The control module detects this code when that signal is higher than its expected range, which can prevent the handshake from completing.
Common causes
Most likely first.
- Signal wire shorted to B+
- Pull-down resistor open
- Connector pins corroded - high contact resistance
Symptoms
- Charge status indicator shows fault
- Charging may not start or interrupts
- Slower-than-expected charge rate
How to diagnose it
- Read charger-related codes and freeze-frame data, and note whether charger B fails to start, interrupts, or charges slowly.
- Inspect charger B signal 1 wiring and connectors for corrosion, loose pins, water intrusion, or contact damage.
- With the system safely isolated according to the vehicle procedure, check whether the signal wire is shorted to battery positive.
- Measure signal 1 at the relevant connector and compare it with the manufacturer's specification to confirm the high reading.
- If the wiring and contacts pass inspection, test the pull-down path and charger B signal input using the manufacturer's diagnostic procedure.
Common fixes
- Clean or repair corroded connector pins and restore secure contact on signal 1.
- Repair a signal 1 wire shorted to battery positive.
- Repair an open or failed pull-down resistor path if testing confirms it.
- Replace or repair charger B only if its signal input remains out of specification with sound wiring.
Can I keep driving?
Charging may not start, may stop, or may be slower than expected; the vehicle may also limit charging operation. Avoid depending on charger B until the handshake fault is resolved, and keep enough charge for the journey.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.