P0812 OBD-II Trouble Code: Reverse Input Circuit

Our certified mechanics come to you · Get a fair and transparent estimate upfront

Red-stars EXCELLENT RATING ON

Cost of diagnosing the P0812 code

P0812 is a diagnostic trouble code (DTC) for "Reverse Input Circuit". This can happen for multiple reasons and a mechanic needs to diagnose the specific cause for this code to be triggered in your situation. Our certified mobile mechanics can come to your home or office to perform the Check Engine Light diagnostic. Once we are able to diagnose the problem, you will be provided with an upfront quote for the recommended fix and receive $20.00 off as a credit towards the repair. All our repairs are backed by our 12-month / 12,000-mile warranty.

Cars Estimate Credit towards follow-up repair Earliest Availability
Ford$20.00
Toyota$20.00
BMW$20.00
SCHEDULE P0812 DIAGNOSTIC Get a fair and transparent estimate upfront

P0812 code definition

The P0812 trouble code identifies a reverse input circuit problem.

What the P0812 code means

This code is triggered when the PCM (Powertrain Control Module) has discovered a problem with the reverse input circuit. When the driver puts their vehicle in reverse, they do so by using the shifter, which is then energized. The PCM monitors this process to ensure the voltage from this switch falls within an acceptable range predetermined by the manufacturer.

When the PCM detects an irregular amount of voltage or that there was resistance from the reverse input circuit, the P0812 code will be stored.

What causes the P0812 code?

There are three main causes that usually result in a P0812 code being stored:

  • The reverse input switch may be defective
  • Wiring that facilitates the use of the reverse input switch may be short or open
  • This wiring could also be damaged In very rare scenarios, the PCM may actually be to blame and storing codes wrongfully, but it’s more likely to be one of the above (the first is actually the most common culprit).

What are the symptoms of the P0812 code?

This code will almost always coincide with the Check Engine light coming on. However, some models are designed to only activate this light once the problem has been detected at least two or three times. In some cases, the backup lamps may also quit working.

How does a mechanic diagnose the P0812 code?

In order to diagnose the problem behind this code, the mechanic will need to:

  • Use an OBD-II scanner to download all the stored codes from the PCM
  • Capture this data on a freeze frame and record all relevant information like the time and frequency with which they occurred
  • Diagnose and repair any other problems that were identified through stored codes on the PCM
  • Carry out an examination of the wiring and connectors to look for loose connectors or corrosion
  • Check for voltage on the input switch
  • Check to see if the fuse needs to be replaced
  • Put the vehicle in reverse and check the voltage on the output side of the input switch
  • Confirm resistance and continuity between the reverse input switch and the PCM Before testing any circuitry, the mechanic should disconnect any related control modules. Doing so will prevent potential damage to the PCM and other costly repairs.

Common mistakes when diagnosing the P0812 code

As we mentioned above, one of the symptoms of this code is that the backup lamp may quit working. This is usually because of a short in the wiring, though it could also have to do with a faulty reverse input switch or bad connectors. However, a hasty mechanic may immediately assume that the problem has to do with the lamp bulbs.

How serious is the P0812 code?

There is nothing inherently dangerous about the P0812 code. That being said, if it results in the backup lamps burning out, the driver will need to get around with them. That can be dangerous as other drivers won’t have forewarning when the automobile is backing up. Getting caught with this problem could earn the owner a ticket, too, one that will probably cost a lot more than just going in for repairs.

What repairs can fix the P0812 code?

Repairing a malfunctioning reverse input circuit will usually involve some combination of the following:

Additional comments for consideration regarding the P0812 code

When carrying out repairs, the manufacturer’s diagram for the specific make and model should be used to make sense of the circuits that need to be tested. If the vehicle has an automatic transmission, this switch is usually part of a neutral safety switch or manual lever position sensor. With manual transmissions, the switch may be threaded by the gear shifter to the transmission housing.

Need help with a P0812 code?

YourMechanic offers certified mobile mechanics who will come to your home or office to diagnose and repair your vehicle. Get a quote and book an appointment online or speak to a service advisor at 1-800-701-6230.

trouble codes
P0812
Check Engine Light

No more waiting rooms! Our mechanics will come to you to diagnose and fix the P0812 code.

SCHEDULE P0812 DIAGNOSTIC
Get a $20 credit for the follow-up repair

Recent Check Engine Light is on Inspection reviews

Excellent Rating


YourMechanic Check Engine Light is on Inspection Service

Average Rating

4.8/5

Number of Reviews

5,583

Rating Summary
5,159
204
50
34
136
5,159
204
50
34
136

Matt

16 years of experience
35 reviews
Matt
16 years of experience
Jeep Compass - Check Engine Light is on Inspection - Holly Springs, North Carolina
Matt was awesome! Very knowledgeable, thorough. Really knows his stuff. Best part was his level of interaction and being able to ask him questions directly. You just don’t get that at the shops. Will definitely be using this service again and requesting Matt for all future jobs. Thanks again, Matt!

Matthew

32 years of experience
828 reviews
Matthew
32 years of experience
Land Rover LR2 - Check Engine Light is on - Hampton, Virginia
Matt is my go-to mechanic. Always professional and explains in detail what the problem is and how it’s being fixed. Highly recommend.

Richard

16 years of experience
115 reviews
Richard
16 years of experience
Honda Accord - Check Engine Light is on - San Ramon, California
Richard is Polite and skilled in inspecting the issues. I do recommend him for doing diagnostics before giving your car to the garage.

Michael

15 years of experience
565 reviews
Michael
15 years of experience
Chevrolet Avalanche 1500 - Check Engine Light is on - Marietta, Georgia
What professional handled himself well understood what was wrong with the car corrected it immediately and was on time


More related articles

Related questions

I had a p0405 get code replaced egr valve, map sensor,mad sensor, and PCv valve just to be safe but still getting the code why?

The code P0405 and a rough idle is most likely due to carbon getting into the EGR pintle. This will hold the EGR open. When you are getting the rough idle you should shut off engine and remove EGR valve....

Code P02A9 Cylinder 4 Balance-Fuel Trim at Limit

The code definition specifically indicates the number four fuel injector is leaking. Fuel trims are used to indicate how much the PCM (powertrain control module) needs to adjust the fuel duty cycle to maintain the proper air fuel ratio. Duty...

Check engine light

This is true, but there are countless other reasons for an illuminated Check Engine Light as well. A loose gas cap will typically set an evaporative emissions (EVAP) system code, such as P0440 or P0455. The EVAP system...

How can we help?

Our service team is available 7 days a week, Monday - Friday from 6 AM to 5 PM PST, Saturday - Sunday 7 AM - 4 PM PST.

1 (855) 347-2779 · hi@yourmechanic.com