P2195 is a general OBD2 code that indicates that the signal coming from your Mercury Montego’s 1’st O2 sensor on Bank 1 Sensor 1 is stuck lean.
DTC P2195 is a general code, which means that it has the same meaning for any make, model, or year. It is most typically caused by a bad O2 sensor, but there can A LOT of issues that can cause this code.
P2195 Symptoms: Mercury Montego
The symptoms associated with P2195 can be varied. Often, the check engine light will be the only symptom.
- Check engine light
- Rough running engine
- Hard/Rough start
- Difficulty idling
P2195 Common Causes: Mercury Montego
- Oxygen Sensor– The oxygen sensor could be bad, or the wiring going to/from it could have issues. The wiring that goes to all of the O2 sensors is some of the most error prone on any vehicle. It gets more exposure to the elements and heat, which can lead to an open/short situation.
- Bad Sensor– Your Montego’s PCM relies on the MAF, ECT, A/F sensors to help it adjust the air/fuel ratio. When they go bad, it may force the air/fuel mixture to lean out, which in turn can throw P2195.
- Vacuum Leak– A vacuum leak allows UNMETERED air to enter into the combustion chamber, changing the air/fuel mixture.
- Fuel System– A bad fuel injector or the wrong fuel pressure can cause P2195.
- Exhaust Leak– An exhaust leak allows the exhaust to exit somewhere other than the tailpipes. If there is too much exhaust that is allowed to leave, it’ll show up as a lean condition.
Here are some diagnostic steps that you can use to diagnose this code in your Montego from home.
Capture the Short/Long Term Fuel Trim Values
If you happen to have access to a scan tool, you can use it to capture the short and long term fuel trim values. You’ll need to make sure that the engine is warmed up before you do this.
Doing this will help you determine if the O2 sensor is operating within spec without having to do any looking under the hood.
While this isn’t a skill most DIY mechanics have, the concept is simple, and you can learn enough to use fuel trim to your advantage by watching this 11 minute video.
Swap Test (Won’t Work on 4 Cylinder Engines)
If you happen to have a V6, V8, or V10 engine, you can do the “swap test” to determine if the bank 1 sensor 1 oxygen sensor is bad. Here’s what you do.
- Clear the codes with your scanner.
- Swap the Bank 2 Sensor 1 O2 sensor with the Bank 1 Sensor 1.
- Run the engine until the check engine light comes back on.
- If the code changes to P2197 (which indicates the O2 sensor on Bank 2 is stuck lean), that is enough proof that you need a new Oxygen sensor.
- If the code remains P2195, you’ll need to continue pursuing your diagnosis, knowing that both O2 sensors are working fine.
Check the O2 Sensor Harness
You can use a multimeter to check for any short or open circuits at the wiring harness. A quick visual inspection can often tell you if there is something wrong, but not in the way the use of a multimeter will.
Often a worn or brittle vacuum line will allow unmetered air into your Montego’s engine. When this happens, it creates a lean condition.
You can test for a vacuum leak around the vacuum lines and the intake manifold. A common method is to spray carb cleaner around the intake/vacuum lines. When the spot is found the engine will rev higher.
Obviously, carb cleaner is super flammable. So be CAREFUL. Make sure you have a form of fire suppression available to you.
If you have an engine with 2 banks (not an inline engine) and you’re getting P2195 without getting P2197, it could mean that an injector has gone bad.
If you have an inline engine (or an engine that has P2195 +P2197), check the fuel pressure compared to the factory specs.
If you’ve looked over all of the items listed above, and you still haven’t diagnosed P2195 in your vehicle, don’t give up.
- Take a look at the MAF and IAT sensors. They could be telling the engine the wrong amount of air is entering the combustion chamber.
- Check to see if there are any TSB’s for your engine and model year.
There are a lot of issues that can cause P2195 in the Mercury Montego, you’ll more than likely be replacing an oxygen sensor though. Good luck!