Mercury Mariner P0122: TPS “A” Circuit Low Input

by

P0122 is a common trouble code with the Mercury Mariner. It’s an OBDII code that references issues with the Throttle Position Sensor (TPS). It is relatively serious problem since it can leave your vehicle stranded or severely limited.

 

Mercury Mariner P0122 Diagnosis

 

OBDII code P0122 is a serious problem that requires serious attention. Diagnosing it can be tricky without a good scanner and the knowledge of what you are doing. There’s a YouTube video below that shows how to go about diagnosis with a scanner.

 

 

P0122 Definition

P0122 will trigger in your Mercury Mariner if it’s TPS “A” circuit is reporting a voltage number that is too low. It’s a general powertrain code, which means that it has the same meaning regardless of who manufactured the vehicles (1996+).

 

Mercury Mariner P0122 Symptoms

Mariner P0122 OBDII Code

The symptoms of P0122 are going to vary by year and model, but they certainly are going to cause noticeable changes in the way that your Mariner runs. Without a proper signal from the TPS, your vehicle will compensate in a number of ways.

Here are the most common symptoms of P0122:

  • Throttle Response– It’ll hardly respond to the throttle at all. This limited power is a failsafe to keep the vehicle able to move, but not super fast. Since the ECM won’t really know how much throttle response is actually happening when you push the gas.
  • Idle Speed Issues– Without knowing exactly where the throttle is, the Mariner’s computer may have a difficult time getting the idle speed just right.

P0122 Causes- Mariner

P0122 Mercury Mariner

There are a few issues that cause P0122. They are:

  • Wiring Issues– Since the TPS is so accessible, a great place to start is to do a visual inspection of the wiring and harness coming to it from the engine’s computer. Is there any damage? Here’s a great article on diagnosing a short circuit.
  • Bad TPS– There is a YouTube video above on how to diagnose a TPS sensor. If you need one they are pretty inexpensive on Amazon.
  • TPS not properly mounted– While not very common, it is possible the TPS sensor was not mounted properly. If you have recently replaced it and are getting P0122, it’s a good idea to check the replacement sensor instructions and see if they mention this at all.

 

Mercury Mariner P0122 Diagnosis

A good mechanic will utilize a scanner to diagnose when the codes were set and reset them. They’ll then see if the problem comes back.

If it all checks out and the code comes back, they may go ahead and replace the TPS sensor in question. Most of the time, the problem when P0122 is thrown will be the TPS sensor itself. It no longer is accurately tracking how hard the fuel pedal is being pushed.

Diagnosing the issue with a scanner or having a mechanic take a look can save the expense of buying a TPS sensor that your Mariner does not actually need.

Good luck diagnosing P0122 in your Mercury Mariner. If there is anything that you would like to add, please leave a comment below.