How To Test The 1998 Volvo S70 MAF Sensor With A Multimeter

TEST 3: Testing The 2nd Ground Circuit

In this section, we're gonna' make sure that the fuel injection computer is providing sensor Ground to the MAF sensor.

The wire labeled with the #2 (in the photo above) is the one that provides Ground.

We'll also do a simple multimeter voltage test to confirm that the fuel injection computer is providing this Ground.

NOTE: Be careful and take extreme care not to short-circuit this wire to battery power (as you're probing it) or you'll damage your Volvo's fuel injection computer. The multimeter voltage test, indicated below, is a safe way to test this Ground circuit.

These are the test steps:

1. 1

   Place your multimeter in Volts DC mode and turn the key to its OFF position.

2. 2

   Probe the wire labeled with the #2 with the black multimeter test lead and using an appropriate tool.

3. 3

   Connect the red multimeter probe to the battery positive (+) post.

4. 4

   The multimeter should read 10 to 12 Volts DC if Ground is available.

Let's interpret your test result:

CASE 1: Your multimeter registered 10 to 12 Volts DC. This is the correct and expected test result.

Your next step is to go to: TEST 4: Testing The MAF Signal With A Multimeter.

CASE 2: Your multimeter DID NOT register 10 to 12 Volts DC. This test result tells you that the fuel injection computer is not providing Ground to the MAF sensor in this circuit. Without this Ground, the MAF sensor will not function.

Your next step is to find out why this Ground is missing and restore it.

TEST 4: Testing The MAF Signal With A Multimeter

Now that the basics have been checked, we'll check the MAF signal coming out of the sensor and going to the fuel injection computer.

The wire labeled with the #4 (in the photo above) is the one that carries the MAF signal to the fuel injection computer.

As mentioned at the beginning of the tutorial, the MAF sensor produces a simple voltage signal that can be measured with a multimeter in Volts DC mode.

When the engine is at idle, the voltage value will be low. When the engine is accelerated, the voltage value will increase.

In 9 cases out of 10, when your Volvo's MAF sensor fails, it will produce a voltage value that will not increase or decrease as the engine is accelerated or decelerated. This is how you'll know that your Volvo S70's MAF sensor is defective and needs to be replaced.

NOTE: To test the MAF signal, the MAF sensor must be connected to its electrical connector. You'll need to use a back-probe or a wire piercing probe to access the MAF signal. You can see an example of a wire piercing probe here: Wire Piercing Probe.

OK, let's get started:

1. 1

   Place your multimeter in Volts DC mode.

2. 2

   Probe the wire labeled with the #4 with the red multimeter test lead and using an appropriate tool.

3. 3

   Connect the black multimeter probe to the battery negative (-) post.

4. 5

   Start the engine and let it idle for about 5 minutes till it reaches its normal operating temperature.

5. 6

   Accelerate the engine as you watch the multimeter's voltage readings.
   
   The voltage value reading should increase when you accelerate the engine and should decrease when you decelerate it.

Let's interpret your test result:

CASE 1: The voltage reading increased and decreased as indicated. This is the correct and expected test result and tells you that the MAF sensor (on your Volvo S70) is working correctly.

CASE 2: The voltage reading DID NOT increase or decrease as indicated. This test result lets you know that your Volvo S70's MAF sensor is defective and needs to be replaced.