P06A9: Sensor Reference Voltage D Circuit Range/Performance

The engine module feeds sensors from several regulated 5 V reference circuits; a short at one sensor pulls the whole circuit down and all its sensors report at once – unplug them one by one to find the culprit. P06A9 is the range/performance check of reference circuit D. No manufacturer document available to us uses this code; the description follows the other reference circuits. Ford checks circuits A–C this way (below 4.7 V or above 5.2 V); GM reports circuit D under the collective code P06A3, where pedal sensor 1 and the throttle sensors are typically connected – so electronic throttle limp mode is likely.

Symptoms

• Check engine light
• Several sensor codes at once
• Reduced power or limp mode
• Possibly starting problems

Most likely causes

• Short in the wire or sensor of a connected sensor
• Chafing or water in harness or connector
• A connected sensor faulty internally
• Module internal voltage regulator or components

What to check, in order

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

1. Check the battery and grounds
2. Compare the reading with other engine data while varying the engine speed.
3. Clear the code and see if it returns
4. If it is a reference voltage code, disconnect sensors one at a time and see if the voltage recovers
5. Check whether a software update is available
6. Do not replace the control module without a full diagnosis

Good to know

• Repair difficulty: medium
• It can trigger limp mode.
• It affects emissions.

What each character of P06A9 means

• P: Powertrain: engine and transmission
• 0: Generic code: same on every make
• 6: Control modules and outputs
• A9: Specific fault in that system

Frequently asked questions

Can I keep driving with code P06A9?

It depends on the symptoms. If the car is running normally you can go to a repair shop; if it goes into limp mode, drive as little as possible.

What causes code P06A9?

The most common causes are: short in the wire or sensor of a connected sensor; chafing or water in harness or connector; a connected sensor faulty internally.

Related codes

• P06A3Sensor Reference Voltage D Circuit/Open
• P06A4Sensor Reference Voltage D Circuit Low
• P06A5Sensor Reference Voltage D Circuit High
• P06A8Sensor Reference Voltage C Circuit Range/Performance
• P06A6Sensor Reference Voltage A Circuit Range/Performance

Sources

• law.cornell.edu: 13 CCR 1968.2
• newtonnet.co.uk: fordobd2012
• gsi.ext.gm.com: 18OBDG03A 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.