P0105 - Manifold Absolute Pressure/Barometric Pressure Circuit Problem. This trouble code is simply telling you that the fuel injection computer, on your 1995-1998 1.5L Toyota Tercel, is not seeing the MAP sensor's voltage signal decrease under engine load.
To understand why this trouble code is set, here's a brief explanation of how the MAP sensor works:
The MAP sensor produces a voltage signal that decreases/increases depending on the amount of vacuum in the intake manifold.
When the engine is at idle, the manifold vacuum is lower and the MAP sensor produces a higher voltage signal. When the engine is under load (like when accelerating the vehicle on the highway), the manifold vacuum is higher and the MAP sensor produces a lower voltage signal.
If the your Toyota Tercel's fuel injection computer does not receive a varying MAP voltage signal, it sets a P0105 -MAP Sensor Circuit Malfunction trouble code.
What Causes A Trouble Code P0105?
There are several things that can cause a trouble code P0105, on your 1995-1998 1.5L Toyota Tercel. Here's a basic list of the problems that can cause it:
- On open-circuit or short-circuit problem in the MAP signal wire (between the MAP sensor connector and the fuel injection computer connector).
- The MAP sensor is bad and is stuck producing one voltage value.
- The MAP sensor connector is damaged and is making a bad connection.
- The vacuum hose that connects the MAP sensor to the intake manifold may be cracked, damaged, or kinked.
- The engine has compression problems caused by burned valves or worn piston rings.
- Timing belt is not synchronized.
- The fuel pump is failing and fuel pressure is lower than the specified fuel pressure.
Symptoms Of A Trouble Code P0105
You'll see one or more of the following symptoms when the MAP sensor is causing a trouble code P0105:
- Poor engine performance.
- Rough idle.
- Black smoke coming out of the tailpipe when the engine is running or accelerated.
- Bad gas mileage.
- Rotten egg smell coming out of the tailpipe when the engine is running.
- Engine does not start.
- Engine starts but stalls.
- The check engine light is on (also known as the malfunction indicator lamp).
How To Diagnose And Repair A P0105 Trouble Code
The 1995-1998 1.5L Toyota Tercel's MAP sensor is an expensive fuel injection component. So testing it before replacing it, to make sure that it's bad, is a good idea.
Before testing the actual MAP sensor, make sure that:
- The MAP sensor's vacuum hose is not cracked, damaged, or kinked.
- The MAP sensor's vacuum hose is connected to the correct vacuum port on the intake manifold.
- The MAP sensor's vacuum hose has vacuum with the engine running.
- The MAP sensor's connector is not damaged.
Testing the MAP sensor simply involves connecting a multimeter to its MAP signal wire and then applying vacuum to it. If the MAP sensor is good, you'll see:
- The MAP voltage signal should decrease when you apply vacuum.
- The MAP voltage signal should increase when you release vacuum.
If the MAP sensor stays stuck producing one voltage value as you apply/release vacuum to it, then the next steps are to make sure that it's receving 5 Volts DC and Ground from your 1.5L Toyota Tercel's fuel injection computer.
Now, you can conclude that the MAP sensor is bad and causing the P0105 trouble code (and needs to be replaced) only if you have:
- Confirmed that its voltage signal does not decrease/increase as you apply release vacuum to it.
- Confirmed that the MAP sensor is receiving 5 Volts DC.
- Confirmed that the MAP sensor is receiving Ground.
The following tutorial explains how to test the MAP sensor:
More 1.5L Toyota Tutorials
You can find a complete list of tutorial for the 1.5L Toyota Tercel in this index: Toyota 1.5L Index Of Articles.
Here's a small sample of the tutorials you'll find in the index:
- How To Test The Ignitor -Step By Step (1995-1996 1.5L Toyota Tercel).
- How To Test Engine Compression (1.5L Toyota Tercel).
- How To Test The Fuel Injectors (1995-1996 1.5L Toyota Tercel).
- How To Test For A Blown Head Gasket (1.5L Toyota Tercel).
If this info saved the day, buy me a beer!