My 2001 2500 Duramax governs it's self down to about 55 mph when I'm going about 65 mph on the freeway with a load. It does this without warning and then takes off again after about 1 minute. Code 234 turbo overboost showes on the diagnostic. Is there a fix for this?

What mods do you have?

A 4" exhaust with a K&N filter.

Do you have the airbox update yet? There is an update to change the design of the airbox and seal off the fender hole, replace the MAF if needed, and reflash the PCM. It is due to contamination of the MAF from water and debris.

6.6L LB7 Duramax Diesel DTC P0234, P0106 #PI00036 - (Jun 18, 2002)

6.6L LB7 Duramax Diesel DTC P0234, P0106

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When servicing the vehicle with the VIN you entered, the following diagnosis might be helpful if the vehicle exhibits the described symptoms.

<A href="http://service.gm.com/servlets/BlobShtml?ShtmlFile=894358&psdid=210&evc=sm#ss1-894358">Condition/Concern:

DTCs P0234 and or P0106

<A href="http://service.gm.com/servlets/BlobShtml?ShtmlFile=894358&psdid=210&evc=sm#ss2-894358">Recommendation/Instructions:

<LI type=1>Verify all intake air duct work clamps are securely clamped and correctly positioned. Refer to SI documents 697123 and 741002 for locations on clamps and duct work. <LI type=1>Verify connection to baro sensor is good. If P0106 is reoccuring, replace baro sensor.
If all duct work is secure, and the trouble tree for the associated DTC leads to NTF, and if the DTC is set only when a load is placed on the engine, reflash the PCM with calibration 15076144 or higher.
Please follow this diagnosis process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed. If these steps do not resolve the condition, please contact GM TAC for further diagnostic assistance. This diagnostic approach was developed for the vehicle with the VIN you entered and should not be automatically be used for other vehicles with similar symptoms.

Decreased Engine Performance/Power, Filter Minder Indicator On, Possible MIL Illuminated and DTC P0101/P0103 Set (Replace AIr Cleaner/Reprogram ECM) #01-06-04-050 - (Oct 19, 2001)

</TABLE>Decreased Engine Performance/Power, Filter Minder Indicator On, Possible MIL Illuminated and DTC P0101/P0103 Set (Replace Air Cleaner/Reprogram ECM)

2001 Chevrolet and GMC C/K Pickup Models

with 6.6L Duramax™ Diesel Engine (VIN 1 -- RPO LB7)

<A href="http://service.gm.com/servlets/BlobShtml?ShtmlFile=826937&pubid=210&evc=sm#ss1-826937">Condition

Some customers may comment on decreased engine performance/power on the above vehicles with the LB7 Duramax™ Diesel engine. The Malfunction Indicator Lamp (MIL) may be illuminated with DTC P0101/P0103 set. The customer may also note that the "filter minder" on the air cleaner assembly may indicate the filter element needs replacing at very low mileage. These symptoms are more likely to occur when pulling a trailer on wet/slushy roads, but have been reported in heavy rain, at curb weight, during highway driving.

<A href="http://service.gm.com/servlets/BlobShtml?ShtmlFile=826937&pubid=210&evc=sm#ss2-826937">Cause

The LB7 diesel engine creates very high air flow under load. The primary source of inlet air to the engine is through the right front fender. The tires kick up water spray on wet roads which is pulled in with the incoming air from the right fender opening located over the front bumper. This ingested water may soak the airfilter element causing increased restriction. This restriction may activate the "filter minder". If the water continues past the filter, wetting the mass air flow (MAF) sensor, the MIL may illuminate.



Important

If the vehicle is being driven through snowy and/or slushy roads that have been salted, the MAF sensor may be contaminated with soluble road salt.



<A href="http://service.gm.com/servlets/BlobShtml?ShtmlFile=826937&pubid=210&evc=sm#ss3-826937">Correction

Install a revised air cleaner assembly, P/N 25345138, that has a lower incoming air velocity. Also, seal off the right inner fender panel air inlet holes and reprogram the ECM by following the procedure below.

<LI type=1>Open the hood and install fender covers. <LI type=1>Remove the air cleaner assembly hose clamp from the ductwork. <LI type=1>Disconnect the MAF sensor electrical connector. <LI type=1>Remove the air cleaner assembly from the vehicle by pulling upward. <LI type=1>Examine the air cleaner assembly for signs of salt intrusion (white, chalky powder). If signs of salt are present, and the vehicle has set a DTC P0101 or P0103, install the air cleaner assembly by reversing the three steps above. Refer to the Engine Controls sub-section of the 2001 Service Manual. The diagnostic table for DTC P0101 or DTC P0103 outlines the testing procedure for the MAF sensor. If the diagnostic test indicates a contaminated MAF sensor (out of range), remove the air cleaner again and discard the complete assembly. Otherwise, remove the air cleaner and continue with the next step.

Important

It is critical that the surface you will bond the mastic material to be clean and grease free. Poor preparation could lead to the mastic coming loose and being sucked against the air filter element causing a poor power condition.



<LI type=1>Clean and degrease the right inner fender panel around the holes previously used for air intake.

Important

Depending on the exact size of the mastic material received and the fasteners on the inner fender panel, you may need to trim the mastic material to achieve a good fit.



<LI type=1>Apply the mastic material to the inner fender panel, completely covering and sealing the two holes that the original air cleaner snorkels protruded into. Make sure that the mastic is firmly adhered to the inner fender panel. <LI type=1>Remove the two fasteners retaining the MAF sensor from the original air cleaner and transfer the MAF sensor to the replacement air cleaner. If the MAF sensor was judged to be contaminated in step 5, install a new MAF sensor, GM P/N 88892543, to the replacement air cleaner. <LI type=1>Position the new air cleaner to the mounting tray and firmly seat the push-in retainers. <LI type=1>Attach the air intake hose to the air cleaner assembly and secure the clamp. <LI type=1>Connect the MAF sensor harness to the sensor. <LI type=1>Recalibrate the ECM with the latest update. The calibrations are available from Techline starting September, 2001 on the TIS 2000 version TIS 10/2001 data update or later. Refer to the Tech 2 user guide for specific reprogramming instructions when using the scan tool.
Remove the fender covers and close the hood.
<A href="http://service.gm.com/servlets/BlobShtml?ShtmlFile=826937&pubid=210&evc=sm#ss4-826937">Parts Information

<TABLE width="100%" border=1><TBODY><TR><TH vAlign=bottom align=middle>Part Number

</TH><TH vAlign=bottom align=middle>Description

</TH></TR><TR><TD vAlign=center align=middle>25345138

</TD><TD vAlign=center align=middle>Cleaner Asm, Air

</TD></TR><TR><TD vAlign=center align=middle>88892543

</TD><TD vAlign=center align=middle>Sensor Kit, Mass Airflow

</TD></TR><TR><TD vAlign=center align=middle>25662607

</TD><TD vAlign=center align=middle>Dampening Pad, Mastic

</TD></TR></TBODY></TABLE>

Parts are currently available from GMSPO.

<A href="http://service.gm.com/servlets/BlobShtml?ShtmlFile=826937&pubid=210&evc=sm#ss5-826937">Warranty Information

For vehicles repaired under warranty, use:

<TABLE width="100%" border=1><TBODY><TR><TH vAlign=bottom align=middle>Labor Operation

</TH><TH vAlign=bottom align=middle>Description

</TH><TH vAlign=bottom align=middle>Labor Time

</TH></TR><TR><TD vAlign=center align=middle>J5000

</TD><TD vAlign=center align=middle>Air Cleaner - Replace

</TD><TD vAlign=center align=middle>0.4 hr

</TD></TR><TR><TD vAlign=center align=middle>Add

</TD><TD vAlign=center align=middle>Diagnosis (MAF Sensor)

</TD><TD vAlign=center align=middle>0.0-0.3 hr

</TD></TR><TR><TD vAlign=center align=middle>Add

</TD><TD vAlign=center align=middle>To Replace or Transfer MAF Sensor

</TD><TD vAlign=center align=middle>0.1 hr

</TD></TR><TR><TD vAlign=bottom align=middle>J6355

</TD><TD vAlign=bottom align=middle>Powertrain Controller - Reprogram

</TD><TD vAlign=bottom align=middle>0.5 hr

</TD></TR></TBODY></TABLE>

I'm getting code 234, turbo over-boost. I have a huge K&N filter, I don't think my engine is air starved. It is only under load at 65 mph and above. The engine slows down to aprox. 55 mph for about 1 min. and then takes off again.

The K&N oil can get on the MAF sensor and screw up the readings, which can cause errant codes like this. Take it to a dealer and have it diagnosed properly. You will be happy you did.

Taken fron post above: "If all duct work is secure, and the trouble tree for the associated DTC leads to NTF, and if the DTC is set only when a load is placed on the engine, reflash the PCM with calibration 15076144 or higher."