Ford Focus P1100 Trouble Code – Test your MAF Sensor

When your Focus check engine light is on, it can be a stressful time for any Ford owner. When this annoying trouble code light is illuminated through your Focus instrument cluster, you’ll need a OBDII scan tool to see what the code is. Your OBDII scan tool should be able to retrieve the alphanumeric trouble code, and when Ford Focus P1100 is the problem, you will need to test your mass air flow sensor.

This guide will help you troubleshoot your Ford Focus MAF sensor. To do this you’ll need a digital multimeter to test the circuits wire by wire. Because the Intake Air Temperature is a part of your Focus MAF, there’s a few different ways you can test the air flow meter.

Ford Focus MAF Sensor 1

The specific wording around the Ford Focus P1100 is MAF Circuit Intermittent Voltage Input. This means that there’s either an issue with your MAF wiring or the sensor itself. The mass air flow meter in your Ford is required by your Powertrain Control Module, or PCM to operate the fuel delivery and ignition spark properly.

When this sensor goes bad there’s going to be several issues with your Ford Focus. Today I’ll be showing you how to test this MAF sensor in a 2004 Focus with a 2.0 liter ZETEC engine. Some of these symptoms can range from annoying to problematic, and even prevent your Ford Focus from starting. Here’s just a few Ford Focus problems that can arise from your mass air flow sensor going bad.

Of course one of the first things to check in your 2.0 liter ZETEC engine is to check for air leaks in your air intake piping. This can be done using a spray bottle and soapy water to gently spray onto your piping. You should be able to notice air bubbles to indicate an issue with your leaks in your air intake pipes.

Problems from your Ford Focus P1100 trouble code

Intermittent signal from your Ford mass air flow meter is going to cause your check engine light to turn on. Because your engine computer will not have the information it needs to adjust and deliver the right amount of fuel, there’s other Ford Focus issues that can affect your ZETEC engine.

  • Poor gas mileage
  • Bad engine performance
  • Inconsistent idle
  • Smoke from your tailpipe

Further because your mass air flow sensor dictates the fuel delivery of your 2.0 liter Ford engine, it could run rich ( too much fuel ) or lean ( not enough fuel ) which isn’t good. When your 2.0 liter ZETEC engine doesn’t have enough fuel, engine damage could occur. This can come from engine pinging or pre-detonation which can damage a ring land in your engine. Too much fuel is also a bad condition, because it can artificially raise your exhaust gas temperatures.

This rise in exhaust gas temperatures or EGT can lead to your catalytic converter failing. This is a very expensive part to replace, so when you’ve got a Ford Focus P1100 trouble code it’s a good idea to test your MAF.

MAF Sensor Wiring Diagram – Ford Focus P1100

Because the trouble code is specifically regarding the signal from your Ford MAF being intermittent, there’s a few ways to test this. Before you begin checking your Ford mass air flow sensor, you’ll need to turn your Focus ignition to the “ON” position. Now open your hood and locate your MAF housing, as it’s mounted to your intake piping.

Ford Focus P1100 Trouble Code 12

The first order of business is to check for a power and ground signal at the MAF connector. This is easily done by simply pushing down on the retaining tab and disconnecting the MAF engine harness. Remember that your ignition should be turned to the “ON” position, and that you are checking on the ENGINE harness side of the Ford. You can use the Ford Focus MAF wiring diagram below or even reference the letters stamped on the top of the sensor itself.

The wires you will be checking first is PIN A which should be a switched power signal from your ECU. Put the black probe of your multimeter to a battery ground and use the red lead to check for power at the MAF harness. Remember to never use a ground from your engine harness, as this could lead to engine computer damage.

Ford Focus P1100 Trouble Code 11

If you’ve got power at this wire, the next thing to check is the ground signal. This is PIN C for your MAF ground that your PCM supplies and PIN B which is your chassis ground.

When you have confirmed that your Ford Focus MAF has power and ground, you know that it should be operating correctly. If this checks out the next thing to move onto is your Focus mass air flow meter signal wire. This signal wire is what is causing your Ford Focus P1100 trouble code to crop up.

Because the Ford Focus P1100 check engine code means that there’s an issue with intermittent signal or an occasional lack of signal, you should check your wiring.

Inspect the base of the wiring connector to make sure that there’s no exposed wire or problems with your MAF harness. Improperly seated pins or connectors could also lead to an intermittent issue. Once this part of your Ford Focus MAF checks out, the next part of the test is to check for your MAF signal.

Reconnect your Ford Focus MAF sensor, and clear your engine bay. Start your engine and allow the engine to warm up, which should give you the correct operating temp of your airflow meter.

The wire you will need to pierce is PIN D on your Ford Focus MAF. When your engine is running make sure to keep your hands and tools clear of your engine bay. Measure the signal voltage from the wire at PIN D, which should tell you what signal wire your mass air flow meter is sending to your engine computer.

Increase your engine speed (RPM) and monitor this value at this wire. Make sure there’s no gaps or dips in voltage. You should see this voltage rise slowly and then fall to match the engine RPM. If your Ford Focus MAF sensor is still working and in operational order, you should see the numbers rise and fall slowly without any gaps in voltage.

The other wires to the Ford Focus MAF sensor are listed below, again don’t forget that these letters are stamped on the top of the housing.

  1. Letter F: Air Temp. sensor circuit
  2. Letter D: MAF Signal
  3. Letter C: Ground that the ECM provides
  4. Letter B: Ground
  5. Letter A: 12 Volts
  6. Letter E: Air Temp. sensor circuit

If your Ford mass air flow sensor does not respond correctly, you will need a replacement Focus MAF sensor. Have any questions about this guide on fixing your Ford Focus P1100 trouble code? Leave them for us below and let us know!


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