P08AF: Neutral Position Sensor B Circuit Low

The signal of neutral position sensor B, the second neutral sensor or channel of a manual gearbox, has fallen below its lower electrical limit. Typical reasons are a signal wire shorted to ground, a missing sensor supply or a sensor without output. No manufacturer documents P08AF publicly; the A-sensor codes are documented by Audi (sender G701, three-wire Hall sensor) and by GM on the LT5 Corvette. A GM patent describes the sensor as two Hall elements on the shift shaft feeding a PWM signal to the engine module. CARB 1968.2 (e)(15) requires low/high circuit monitoring of such inputs. High is P08B0, the A-sensor equivalent P086C. Start-stop is usually blocked; the MIL status is left to the manufacturer.

Symptoms

• Start-stop no longer works
• Start system warning in the cluster
• Fault stored without driving complaint

Most likely causes

• Signal wire chafed and shorted to ground
• Sensor supply open
• Sensor B without output
• Water or corrosion in the connector at the gearbox

What to check, in order

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

1. Check the fluid level and condition
2. With the connector unplugged, check whether the signal wire is making contact with ground.
3. Read the input and output speed in live data
4. Check the connector and wiring
5. Check for other related engine codes
6. Consult the manufacturer's procedure for the transmission

Good to know

• Repair difficulty: medium

What each character of P08AF means

• P: Powertrain: engine and transmission
• 0: Generic code: same on every make
• 8: Transmission
• AF: Specific fault in that system

Frequently asked questions

Can I keep driving with code P08AF?

Drive gently to a repair shop. If it slips, you hear clunks, or it loses its gears, do not keep driving.

What causes code P08AF?

The most common causes are: signal wire chafed and shorted to ground; sensor supply open; sensor B without output.

Related codes

• P08ADNeutral Position Sensor B Circuit/Open
• P08AENeutral Position Sensor B Circuit Range/Performance
• P08B0Neutral Position Sensor B Circuit High
• P08B1Neutral Position Sensor B Circuit Intermittent/Erratic
• P086CNeutral Position Sensor A Circuit Low

Sources

• law.cornell.edu: 13 CCR 1968.2
• patents.google.com: en
• static.nhtsa.gov: MC 10244474 0001

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.