Learning how to change a Chevy Express MAP Sensor is a vital part of addressing the OBDII trouble code P0106. This check engine light code signals trouble with your Chevy Express manifold absolute pressure sensor, and it’s specifically titled MAP/Barometric Pressure Circuit Range/Performance.
Today I’ll be showing you how to change a Chevy Express MAP Sensor in a 2003 Chevy Express 2500 HD with the 4.8 liter LR4 engine. When your 4.8L MAP sensor begins to fail or have issues reading the pressure from your intake manifold, your check engine light may turn on in your Express dashboard.
What is the MAP Sensor?
The MAP sensor is a barometric or pressure sensor that’s designed to read the incoming pressure at the intake manifold, and relay this data back to your ECU. This enables your ECU to operate closed loop mode, or the part throttle function that controls your gas mileage.
Along with the OBDII trouble code of P0106, you can also have some other codes that relate to this MAP sensor failure.
- P0107: MAP Sensor Circuit Low Voltage.
- P0108: MAP Sensor Circuit High Voltage.
Where is my Chevy Express MAP Sensor Located?
The three pin manifold absolute pressure sensor is inserted into the top of your intake manifold, and can be serviced through your engine bay. Because your 4.8 liter LR4 engine sits underneath the center console of your Chevy Express van, it may be a bit difficult to reach the sensor but it’s 100% doable.
Our How To change a Chevy Express MAP sensor, you’ll need to remove your coolant overflow tank and MAF sensor and intake tract to reach the sensor. Before you begin our guide on replacing the LR4 MAP sensor, disconnect the negative terminal of your battery to ensure there’s no accidents.
Find and locate the Mass Air Flow Sensor, and disconnect it by pulling the gray retaining clip out of the MAF connector. Unplug this MAF, and go about removing the 10mm bolts that hold the airbox in place. Now that this is loosened, you can disconnect the 10mm bolt that holds the bottom of your coolant overflow tank.
Next you are removing the 10mm bolts that hold the upper radiator fan shroud, there’s six of them in total. Now undo the bolts that run through the top of the upper radiator shroud, and gently massage the shroud out of place.
Now that you have this huge plastic shroud removed, you can reach back through the intake manifold and carefully unplug your Chevy Express MAP Sensor.
Once you have the sensor unplugged, you can gently pry open the plastic tabs that hold it in place. Give a solid pull on the bad MAP sensor, and make sure to try your best to avoid debris or dirt falling into your intake manifold.
To install your new Chevy Express MAP sensor, insert your new unit and depress until the plastic arms clip over the top of the sensor. Using a scan tool, clear your P0106 OBDII trouble code.
I replaced my MAP Sensor but the trouble code won’t go away
Okay, so if you’ve already replaced your 4.8 liter MAP sensor and cleared your OBDII code, and noticed that the code keeps returning, you’ve got to test the wiring. Hopefully you haven’t put the fan shroud back in place, because you’ll now be testing the Chevy Express MAP sensor connector that you unplugged.
To do this, you’ll need a multimeter or voltmeter. Not sure what those things are? Check out our primer on using a multimeter here for a few pointers.
Remember that this part of our How To guide is addressing the CONNECTOR side of your Chevy Express MAP sensor. To do this, your battery will need to be plugged back in and you’ve got to insert the ignition key, and turn to the “ON” position.
Before doing this, make sure you haven’t done anything to your fuel rails. If you for whatever reason removed your intake manifold or fuel rail to reach your MAP sensor, reconnecting your battery and turning the key to the “ON” position will prime your fuel pump.
Unplug your MAP sensor connector, and gently probe the front of PIN A, which is the left most pin with the MAP sensor installed. Placing the black lead of the multimeter to the negative terminal, and the red probe to PIN A you should read 5 volts of power here. If you don’t have 5 volts of power here, make sure your key is set to the ON position.
If power is at PIN A, check PIN C next which would be the right hand side pin with the MAP sensor installed. This wire should be the low reference or the ground signal wire. If you have both power and ground here, chances are your OBDII trouble code is coming from the middle wire which is the signal wire.
Inspect the wire that leads out of PIN B and check it for any damage. If there’s any breaks or splits in the wire, this will affect the signal quality to your ECU. Look for open wire elements, or stripped wires that might be rotting or rusted.
