MAP Sensor location?

LarryMc · December 9, 2006

My truck is a long bed 1998 K1500 with a 305 and auto trans. Mileage is 153,000.

For the last several months I have had the Service Engine Soon light coming on at random intervals. The light will stay on for a few days and will then go off. It seems to be coming on at more frequent intervals lately. Other than the light coming on, the truck runs like a top and starts easily in any conditions.

The code is;

P0401 -- Exhaust Gas Recirculation Flow Insufficient Detected

I have replaced the EGR valve, cleaned the PCV valve, changed plugs, plug wires, distributor cap & rotor, and changed the fuel and air filter.

None of these have made any difference. I have been told that the MAP sensor and/or the MAF (Mass Air Flow) sensor could also cause this code.

I have managed to locate the MAF sensor but for the life of me I cannot find the MAP sensor. Can anyone tell me where it is located on my truck? I have a Haynes manual on order but it hasn't arrived yet.

Thanks for any help,

Larry

keebler · December 10, 2006

My truck is a long bed 1998 K1500 with a 305 and auto trans. Mileage is 153,000.

For the last several months I have had the Service Engine Soon light coming on at random intervals. The light will stay on for a few days and will then go off. It seems to be coming on at more frequent intervals lately. Other than the light coming on, the truck runs like a top and starts easily in any conditions.

The code is;

P0401 -- Exhaust Gas Recirculation Flow Insufficient Detected

I have replaced the EGR valve, cleaned the PCV valve, changed plugs, plug wires, distributor cap & rotor, and changed the fuel and air filter.

None of these have made any difference. I have been told that the MAP sensor and/or the MAF (Mass Air Flow) sensor could also cause this code.

I have managed to locate the MAF sensor but for the life of me I cannot find the MAP sensor. Can anyone tell me where it is located on my truck? I have a Haynes manual on order but it hasn't arrived yet.

Thanks for any help,

Larry

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Larry:

The Vehicle Control Module tests the EGR system during deceleration by momentarily commanding the EGR valve open. The pressure in the intake manifold increases when the EGR valve is open. The VCM monitors the Manifold Absolute Pressure (MAP) sensor signal during the EGR system diagnostic in order to determine the amount of EGR flow. The MAP sensor will detect an increase in manifold pressure as the EGR is cycled ON. If the amount of manifold pressure observed is less than expected by the VCM, a DTC P0401 will be set.

MAP Sensor

The MAP sensor is plugged in to the intake manifold behind the throttle body on the passenger side. Looking from the front of the vehicle, it's hiding behind the air intake tube. You might be able to stand on the passenger side near the firewall and see it better from there.