Sensor Reference Voltage "A" Circuit/Open
What it means
The engine computer (ECU) supplies a steady reference voltage (usually 5 volts) to a group of sensors through a shared circuit called A. The computer detected an open or fault in this circuit, and because several sensors depend on it, codes for different sensors often appear at the same time.
Symptoms4
- Check engine light on with codes for several sensors at once.
- Limp mode with poor accelerator response.
- Hesitation, stalling or hard starting.
- Illogical readings from some sensors on the scan tool.
Possible causes5
- Broken or corroded reference voltage wire or splice point in the harness.
- Loose or corroded engine computer connector.
- Damaged connector at one of the sensors sharing the circuit.
- Wiring damaged by heat, rodents or previous repairs.
- Faulty reference voltage supply inside the engine computer.
How to diagnose5
- Read all codes and note the affected sensors; they usually share the same circuit.
- Identify the sensors fed by circuit A from the manufacturer wiring diagram.
- Measure the reference voltage at each sensor connector with the key on, and compare it with the value at the computer.
- Check wire continuity from the computer to each sensor, focusing on harness splice points.
- Inspect the computer connector for corrosion or loose pins.
How to fix5
- Repair the broken wire or damaged splice.
- Clean and tighten corroded connectors.
- Replace the damaged sensor connector.
- Replace and program the engine computer only if no reference voltage leaves it despite good power supply.
- Clear the codes and confirm sensor readings are normal and the code does not return.
Repair cost
In Saudi riyals; the highlighted part is the expected range for this fault.
The fix is usually a wire or connector repair at low cost; the upper end applies only if the voltage supply inside the computer has failed.
Prices are rough estimates for common cars at independent workshops and vary with the car and the source of the part.
Prices last updated: September 2026
Frequently asked questions
Why did codes for several sensors appear with this code?
Those sensors are fed by the same reference circuit, so when it opens they all lose their signal. Repair the reference circuit before replacing any sensor.
Can I drive with this code?
With caution and only a short distance, because losing the throttle or pedal sensors can put the engine in limp mode or stall it.
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What was wrong? (optional)
This guide is for information only and does not replace an inspection by a qualified technician. If the fault involves brakes, steering, engine temperature, electrics or refrigerant, do not attempt the repair yourself.
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