Testing the MAP sensor on the 1995-1996 1.5L Toyota Tercel is not difficult.
In this tutorial, I'm going to show you how to do it with a multimeter. You'll be able to find out if it's bad or not in three tests.
All of the test steps are explained in detail so that you can get to the bottom of the MAP sensor problem without any complications.
Contents of this tutorial:
Symptoms Of A Bad MAP Sensor
The fuel system, on the 1995-1996 1.5L Toyota Tercel, is a speed density type.
In this type of fuel system, the fuel injection computer needs to know three things to be able to calculate the correct amount of fuel to inject into the engine.
These three things are: engine RPM, intake air temperature, and engine load. It's the MAP sensor that provides the engine load information by measuring the amount of vacuum pressure inside the intake manifold.
With these three pieces of information, the fuel injection computer is able to calculate the amount of air entering the engine. Once it knows the amount of air entering the engine, it can now inject the correct amount of fuel.
Since the MAP sensor is such a critical component of the fuel injection system, when it fails, engine performance is going to suffer drastically.
Since the fuel injection computer monitors the MAP sensor input continuously, when it feels you're going to have the check engine light illuminated buy a specific MAP sensor trouble code. You'll see one of the following:
- DTC P0105 MAP Sensor Circuit.
- DTC P0106 MAP Sensor Range/Performance Problem.
You're also going to see one or more of the following symptoms:
- Rough idle.
- ‘Rotten egg’ smell coming from the exhaust.
- Won't pass the state mandated emissions test.
- Bad gas mileage.
- Lack of power, rough idle, or hesitation.
- Engine cranks a long time before starting.
TEST 1: MAP Sensor Circuit Descriptions
The MAP sensor, on your 1995-1996 1.5L Toyota Tercel, has 3 wires coming out of its connector.
To test the MAP sensor, we need to know which wire is the one that supplies it with 5 Volts DC. Which wire supplies it with Ground. And which wire is the one that transmits the MAP signal voltage to the fuel injection computer.
Below, you'll find a brief description of each of the three wires of the MAP sensor connector:
|MAP Sensor Connector|
|1||Light green with red stripe (LT GRN/RED)||Power (5 Volts DC)|
|2||Pink (PNK)||MAP Signal|
As you're probably already aware, the MAP sensor's job is to inform the fuel injection computer the amount of vacuum that's inside the intake manifold.
The fuel injection computer then uses this information to calculate the amount of load the engine is under.
In a nutshell, the more vacuum the MAP sensor receives from the intake manifold, like when the engine is being accelerated, the smaller the voltage signal it produces.
The less vacuum the MAP sensor receives, like when the engine is just idling, the bigger the voltage signal it produces.
To test the MAP sensor, we're going to manually apply/release vacuum to it to see if its signal decreases/increases.
Generally, when the MAP sensor fails, you'll see that it's voltage signal stays stuck at one voltage value no matter the amount of vacuum that's applied to it.
TEST 1: Testing The MAP Signal With A Multimeter
To get our MAP sensor diagnostic started, we're going to test the MAP signal voltage while we manually apply vacuum to it.
What we'll do is connect the multimeter to the pink (PNK) wire of the MAP sensor connector.
Then we'll apply vacuum to the MAP sensor with a vacuum pump. Now if you don't have a vacuum pump, don't worry. Because you can use your mouth to apply vacuum to the MAP sensor.
If the MAP sensor is working correctly, then the MAP voltage signal should decrease as you apply vacuum to it.
If the MAP sensor is defective, on your 1995-1996 1.5L Toyota Tercel, then you'll notice that the MAP signal voltage will stay stuck in one value no matter how much vacuum you apply to it.
NOTE: If you don't have a vacuum pump you can use your mouth to apply vacuum to the MAP sensor. If you would like to buy a vacuum pump, check out this link: HTOMT 2 In 1 Vacuum Pump Test Set.
IMPORTANT: The manifold absolute pressure (MAP) sensor must remain connected to its electrical connector for this test to function properly. To be able to access the voltage inside the signal wire, you'll need to use either a back probe or a wire piercing probe. You can see an example of this tool here: Wire Piercing Probe.
Disconnect the vacuum hose that is attached to the MAP sensor.
Connect your vacuum pump to the MAP sensor's vacuum inlet port.
Place your multimeter in Volts DC mode.
Connect the red multimeter test lead to the PNK wire of the MAP sensor's connector.
This wire is identified by the number 2 in the photo above.
Remember, the MAP sensor must remain connected to its 3 wire connector.
Ground the black multimeter test lead directly on the battery negative (-) terminal.
Turn the key on but don't start the engine. This will power up the MAP sensor and you should see a reading of 4.7 Volts DC on your multimeter.
Now, apply vacuum to the MAP sensor with the vacuum pump (or your mouth). The voltage signal value should decrease.
If you're using a vacuum pump: At 5 in.Hg → 3.9 Volts. At 10 in.Hg → 3 Volts. At 15 in.Hg → 2.1 Volts. At 20 in.Hg → 1.2 Volts.
Release the vacuum. Once released, your multimeter should show the original voltage value.
Repeat this test step several times making sure that each time the voltage decreases/increases as you apply/release vacuum.
Let's examine your test results:
CASE 1: The MAP voltage signal decreased/increased as you applied/released vacuum. This is the correct test result.
Since the voltage signal decreases/increases as you apply/release vacuum, you can conclude that the MAP sensor, on your 1.5L Toyota Tercel, is functioning correctly.
You can also conclude that the MAP sensor is getting 5 Volts and Ground from the fuel injection computer.
CASE 2: The MAP voltage signal DID NOT decrease/increase as you applied/released vacuum. In the majority of cases, this test result usually indicates that the MAP sensor is defective.
But to be sure that it is bad, we need to make sure that the MAP sensor is getting 5 Volts DC from the fuel injection computer of your Toyota Tercel. For this test go to: TEST 2: Making Sure The MAP Sensor Is Getting 5 Volts.
CASE 3: The multimeter DID NOT register any voltage. In the majority of cases this test results usually indicates that the MAP sensor is defective.
But to be sure that it is defective, we need to make sure that the MAP sensor is getting 5 Volts DC from the fuel injection computer of your Toyota Tercel. For this test go to: TEST 2: Making Sure The MAP Sensor Is Getting 5 Volts.