Engine/Transmission (1998.5 - 2002) Code 0238 boost pressure voltage high

[DavidC]

A few years back I had a check engine light and a 238 code. Removed all connectors for the sensor and fueling box, cleaned and dieelectric greased. Everything appeared to be ok and have not connected the lap top since. The truck has been averaging about 13mpg around town. Today I thought I would connect with the laptop just to check things. To my surprise I have a 238 code and no check engine light. Cleared and it came right back several times. Installed new sensor and same scenario. Unplugged the fueling box and put the map sensor back to stock wiring. Same thing. I thought that the mileage may be a little low but putting around town with stop signs and lights everywhere it is hard to tell. Maybe mileage will be better if I can get rid of this code. Anybody have any ideas?. Looking at the wiring diagrams the sensor wires to the ECM.



Dave

 

[DavidC]

Looks like it is fixed. Went from 12-13mpg to 16. 5 in a short time with a 10 gallon fill up. Same driving conditions.



Dave

 

[EBung]

So a new map fixed it?

 

[DavidC]

No, where the wires come out of the tubing to the map plug the wires became worn and was shorting the 5v supply to the sense wire causing a high voltage to the ECM thinking it had an overboost condition. The third wire is a check engine signal and was not shorted which is why I did not have a check engine light.



Dave

 

[Chief USA]

Try cleaning the IAT sensor and see if that helps your fuel mileage even more.



SmokinDiesel.com Home



CumminsDatabase.com :: IAT Sensor Cleaning

 

[DavidC]

I usually clean the IAT at least once a year especially since I have the exhaust brake. Before the brake it was always clean with the blue sensor. Since the brake install it usually is black and requires cleaning. The increase in my mileage with the boost code was with a 10 gallon fillup, I am sure if I waited for 15 or 20 gallon fillup the mileage would be higher.



Dave

 

[DavidC]

I forgot to mention the fueling box has been set on 3 x 5 during all this.



Dave