P0818Generic code

P0818 Code: Driveline Disconnect Switch Input Circuit

The P0818 code means there is an electrical fault in the circuit of the transmission disconnect switch. The main effect is limited transmission functions. Check the connector and wiring first, because they fail as often as the switch.

Severity
Low
Can I keep driving?
Yes, no immediate risk
Estimated cost
$20 to $250
Difficulty
Medium
System
Transmission
Applies to
All OBD2 vehicles

Updated Reviewed by Renzo Chacca

On this page

What the P0818 code means

On some vehicles, mostly hybrids and 4x4 vehicles set up for towing, a switch disconnects the driveline so the vehicle can be towed or the power takeoff can be used.

It is a switch: the computer sees a high or low voltage depending on its position. A circuit fault, the P0818 code, can come from the switch, the wiring or the power supply.

If the signal fails, the computer does not know whether the driveline is connected, and it may limit some functions.

Always start with the simplest items: fuse, relay and connector. Then check power, ground and signal with the component connected (using back-probes), and finally the continuity of each wire up to the computer. Only if all of that is good should you replace the component.

P0818 code symptoms

  • Check engine light on.
  • Limited transmission functions.

Likely causes of the P0818 code

  1. Damaged or corroded connector. The most frequent cause.
  2. Wiring cut or shorted between the switch and the computer.
  3. Failed switch, open or shorted internally.
  4. Missing power reference. Check whether other sensors are also failing.
  5. Computer. Uncommon; rule out everything above first.

How to diagnose the P0818 code step by step

  1. Read the switch value on the scan tool and compare it with what is expected.
  2. Inspect the connector for corrosion, water or loose pins.
  3. Check power and ground with the key on: a correct reference and less than 0.1 V of drop on the ground.
  4. Measure the signal with the connector plugged in and see whether it changes with the condition.
  5. Do the wiggle test on the harness with the scan tool in graphing mode.
  6. Check the continuity of each wire up to the computer (under 1 ohm).

How to fix the P0818 code

  • Repair the connector or the wiring.
  • Replace the switch if the tests confirm it.
  • Correct the real condition, if there is one.
  • Clear the codes and verify with a road test.

Technical reference data

  • The switch or sensor is powered from the computer: check the manual for the values.
  • These are approximate values: check the manufacturer data for your vehicle.

Brand-specific notes

The letter assignment and the location of the component change from one manufacturer to another, so check the manual for your vehicle.

Frequently asked questions about P0818

What does the P0818 code mean?
It is a generic OBD2 code that means there is an electrical fault in the circuit of the driveline disconnect switch. The cause can be the switch, its wiring or its power supply.
Can I drive with a P0818 code?
Yes, with caution. Some transmission functions may be limited until it is repaired.
Does the switch have to be replaced?
Only if the tests confirm it. The connector and the wiring fail just as often.
What does the disconnect switch do?
On some vehicles, mostly hybrids and 4x4 vehicles set up for towing, a switch disconnects the driveline so the vehicle can be towed or the power takeoff can be used.
How much does it cost to fix P0818?
As a rough guide, between $20 and $250.
Will a P0818 code clear itself?
It can go out if the connection was only loose or damp for a moment. A damaged connector, wire or switch will bring the P0818 code back.
What is the most common cause of P0818?
A damaged or corroded connector. Check it and the wiring before you buy a switch.

Related codes

Questions about the P0818 code

There are no questions about this code yet. Tell us about your case: vehicle, symptoms and what you have already checked.