P0698Generic code

P0698 Code: Sensor Reference Voltage C Circuit Low

The P0698 code means there is a fault in reference voltage C, the 5 volt supply the computer sends to a group of sensors. It often sets several sensor codes at once and frequently puts the vehicle in limp mode. A typical cause is a sensor or a wire in that group shorted to ground.

Severity
High
Can I keep driving?
Yes, but with caution
Estimated cost
$20 to $400
Difficulty
Medium
System
Computer and Outputs
Applies to
All OBD2 vehicles

Updated Reviewed by Renzo Chacca

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What the P0698 code means

The computer powers many sensors (MAP, throttle position, fuel pressure, A/C pressure, camshaft sensors and more) with a 5 volt reference. So that it does not depend on a single supply, it splits the sensors into several groups: reference A, B, C and so on. The P0698 code tells you that reference C is out of range with low voltage.

When one sensor in the group shorts out, it drags down the whole reference. Every sensor in that group sets a code at the same time, and the vehicle can go into limp mode (limited throttle) or even refuse to start. That is why, when several unrelated sensor codes show up together, the reference is the first suspect.

The most effective method is to unplug the sensors in the group one at a time while you measure the reference (or watch the code on the scan tool). When you unplug the guilty sensor, the voltage returns to about 5 volts.

To confirm the fault, unplug the suspect sensor with the key on and watch what happens to the reading or the code. If the value jumps to the opposite extreme, the wiring is fine and the sensor is the part pulling the signal to ground. If nothing changes, look for the short in the wire itself, starting where the harness rubs against the engine, the chassis or the exhaust.

P0698 code symptoms

  • Several unrelated sensor codes at once.
  • Limp mode with limited power.
  • Erratic gauges on the dash (on some vehicles).
  • The engine may not start.

Likely causes of the P0698 code

  1. Sensor in the group shorted internally. The most frequent cause, often the A/C pressure sensor, the throttle sensor or the fuel pressure sensor.
  2. Reference wire shorted to ground from rubbing.
  3. Connector with water, which creates a path to ground.
  4. Computer. Uncommon.

How to diagnose the P0698 code step by step

  1. Read all the codes and identify which sensors are affected, since they share the reference.
  2. Measure reference C at one of the sensors in the group with the key on. It should read 4.8 to 5.1 volts.
  3. Unplug the sensors in the group one at a time until the reference returns to 5 volts. The last one you unplugged is the culprit.
  4. If it does not recover, check the wiring and the splices of the reference circuit.
  5. Look up the wiring diagram to find out which sensors share the reference on your vehicle.

How to fix the P0698 code

  • Replace the shorted sensor.
  • Repair the damaged wire or splice.
  • Clear the codes for all the affected sensors, including the P0698 code, and verify the repair.

Technical reference data

  • Reference voltage: 4.8 to 5.1 volts.
  • Each reference group powers several sensors.
  • Reference values only: check the manufacturer data for your vehicle.

Brand-specific notes

The source points out that on some brands specific sensors are the usual suspects, so start your search there.

P0698 on GM

On GM, the 5 volt reference shared by the A/C pressure sensor and the throttle sensor is a classic cause of limp mode.

P0698 on Ford

On Ford, the fuel pressure sensor or the MAP sensor often pulls the reference down.

P0698 on Dodge

On Dodge, the fuel pressure sensor or the MAP sensor often pulls the reference down.

Frequently asked questions about P0698

What does the P0698 code mean?
It means reference voltage C, the 5 volt supply shared by a group of sensors, has a fault. The typical cause is a sensor or a wire in that group shorted to ground.
Can I drive with a P0698 code?
Only with caution. The vehicle can go into limp mode or shut off, so it is best to get it diagnosed soon.
Why do so many codes show up at once?
Because every sensor in the group shares the same 5 volt supply. When the reference drops or goes out of range, they all set a code together.
Is it the computer?
Rarely. Almost always it is a sensor or a wire in the group.
How much does it cost to fix P0698?
Between $20 and $400. It can cost more if the computer turns out to be damaged.
What is the most common cause of P0698?
A sensor in the group that has shorted internally, or a reference wire that rubbed through and touched ground or 12 volts. Unplug the sensors one by one to find it.

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