P0812 OBD-II Trouble Code: Reverse Input Circuit

Our certified mechanics come to you · 12-month, 12,000-mile warranty

SCHEDULE P0812 DIAGNOSTIC 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 for $70.00. Once we are able to diagnose the problem, you will be provided with an upfront quote for the recommended fix and receive $30.00 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$70.00$30.00
Toyota$70.00$30.00
BMW$70.00$30.00
SCHEDULE P0812 DIAGNOSTIC Get a fair and transparent estimate upfront

Check Engine Light

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
Check Engine Light
P0812

Fast and easy Check Engine Light is on Inspection service at your home or office.

SCHEDULE P0812 DIAGNOSTIC
Get a fair and transparent estimate upfront

Recent Check Engine Light is on Inspection reviews

Excellent Rating


YourMechanic Check Engine Light is on Inspection Service

Average Rating

4.5/5

Number of Reviews

3,696

Rating Summary
3,372
162
42
24
96
3,372
162
42
24
96

Jason

17 years of experience
69 reviews
Jason
17 years of experience
Friendly and knowledgable about what he does found what was wrong I recommend him
2007 MAZDA 3 - CHECK ENGINE LIGHT IS ON - FRESNO, CALIFORNIA

John

16 years of experience
118 reviews
John
16 years of experience
He arrived early and asked if I would prefer him to start earlier or wait until the actual appointment time, which was so generous! I did not have to wait in the heat while he worked on the car, and instead sat inside my home in the ac as he offered to call when he was finished. John is very knowledgeable and very friendly. Highly reccomend him as alot of men in the car industry take advantage of women, I had no doubt John was being honest and as helpful as can be!
2010 CHEVROLET MALIBU - CHECK ENGINE LIGHT IS ON - AUSTIN, TEXAS

Rodney

33 years of experience
336 reviews
Rodney
33 years of experience
Very prompt and helpful! Explained my options and let me know what to expect in order to fix the problem.
2007 TOYOTA PRIUS - CHECK ENGINE LIGHT IS ON - EL MACERO, CALIFORNIA

Matthew

30 years of experience
403 reviews
Matthew
30 years of experience
He showed up earlier for his appointement with was great!! Very knowledgeable and respectful. Finished job in a timely fashion!
2009 NISSAN ROGUE - CHECK ENGINE LIGHT IS ON - NORFOLK, VIRGINIA

More related articles

P0240 OBD-II Trouble Code: Turbocharger Boost Sensor B Circuit Range/Performance
P0240 code definition Turbocharger Boost Sensor B Circuit Range/Performance What the P0240 code means P0240 is an OBD-II generic code triggered when the Engine Control Module (ECM) detects the intake boost...
How to Buy Fuel Treatments
Adding a fuel additive to your gas tank when you fill up is one way to clean vital engine parts of deposits, improve the performance of your engine,...
How to Avoid Back Pain in a Car
If you have back problems, sitting in a car for an extended period of time can be excruciating. Even without back problems, you could experience discomfort and soreness from...

Related questions

Q: Does the VIN number have to be in the ECM for the vehicle to run?

Some new ECMs will give you a certain amount of free starts before it will not start unless the VIN is added. I am not sure if this is the case with your ECM but you have a dealer telling...

Q: 2004 Mazda 2 DY3W ODB II reader error codes P0031,P0841,P0351,P0733,P0715....what needs to be repaired?

I will explain each code in turn. To resolve all codes, the recommended service to request is a check engine light diagnostic. If you request that service, the responding certified mechanic will get this taken care of for you. ...

Q: Prnds flashing lights anb p0777 code

Hello. For this vehicle, it appears that the solenoids are located inside the transmission. For many vehicles the transmission control solenoids are bolted to the exterior of the transmission, however for this vehicle the solenoids are part of the transmission...

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.

1-800-701-6230 · hi@yourmechanic.com