Subscribe to the Free
Newsletter

Top Tech - Diesel Tech Questions

You've Got Questions? We've Got Answers!

Bruce W. Smith
Apr 23, 2016
Photographers: Bruce W. Smith
Photo 2/6   |   003 Reading DTC Codes
Reading diagnostic trouble codes (DTCs) is easy. Diagnosing and fixing the conditions they’re associated with takes patience and a thorough understanding of the systems related to the codes in question.
Chasing Illusive DTCs
My local diesel shop seems to be baffled by what is causing my ’11 6.7L Ram 2500 Mega Cab to keep throwing a P0191 (fuel rail pressure sensor circuit) code. The tech has replaced the rail pressure sensor four times, and the code still exists. Very frustrated with the mechanic and this ongoing problem!
Leo Thompson
-via email
Oregon Fuel Injection has seen this behavior before, where customers come in after someone else tried to fix a diagnostic trouble code and failed. OFI technicians say it’s critical to follow the diagnostic troubleshooting tree closely. The first part of the troubleshooting for this particular code says: “Note: If there are any EGR, turbocharger, or intake system DTCs present, repair those DTCs before proceeding.”
OFI techs recently received several other codes while diagnosing a P0191 DTC in a customer’s truck, including a P2609 intake air heater code, which was fixed by replacing the intake-air-heater relay. They cleared that code, but the P0191 didn’t reset. “It seems that an engine code is being triggered whenever an emissions-related DTC is present,” says OFI’s Mark Gotchall. “But the truck will not go into the customary ‘limp mode’ for the offending emissions code.”
Whether you are a certified diesel tech or DIYer, a top-shelf scan tool and having access to and carefully reading a vehicle’s diagnostic documents are a must for correctly troubleshooting problems.
Photo 3/6   |   004 Warranty Auto BWS3551
The Federal Emission Control System Warranty covers a long list of a diesel truck’s drivetrain and emissions-related parts for 8 years or 80,000 miles.
Thank the Emissions Warranty
The Allison transmission in my ’10 GMC Sierra 2500HD 4x4 is starting to act a little weird, as in not downshifting from Sixth to Fifth when I’m out on the interstate, shifting a little harsh around town, and slipping for a few seconds from time to time. There haven’t been any diagnostic trouble codes, and the problems happen sporadically. The truck’s 5-year, 100,000-mile powertrain warranty is now expired by years. I’m hoping this isn’t a costly problem and that it’s one I can fix myself.
Chuck B
-via the Internet
This sounds like a transmission-control-module issue. If it is, it’ll be the cheapest transmission fix you’ll ever have: Take your truck to a GM dealership. Among the reading materials that were loaded into the glovebox when your truck was purchased is the Federal Emission Control System Warranty, which says “If any emission-related part on your vehicle is defective, GM will repair or replace it.”
Included in the verbiage is this little nugget: “For 8 years or 80,000 miles, whichever comes first: If the catalytic converter, vehicle powertrain control module, transmission control module, or other onboard emissions diagnostic device, including emission-related software, is found to be defective, GM will repair or replace it under the Federal Emission Control System Warranty.”
While the list of individual parts covered by this warranty is long, it’s good reading material that can be a money saver in situations like yours. Ford and Ram Truck have similar warranty coverage.
Seatbelt Chimes Are Ringing!
I am new to the diesel scene. I purchased a 5.9L ’06 Dodge Ram 2500 regular cab with 182,000 miles on it to use as my work truck and weekend toy hauler. The “Wait To Start” warning came on and the seatbelt chime started dinging. Is this a serious issue?
Marc Hampson
-via email
If the seatbelt chime sounds 10 times while the Wait To Start indicator is illuminated, that’s indicative of diagnostic trouble codes P1222/P1223, which, according to our friends at Oregon Fuel Injection, are associated with excessive injector return. The return is calculated based on the fuel control actuator’s amperage. Any cause for excess return, such as under-torqued connector-tube nuts, damaged connector tubes, worn injectors, or a sticky FCA will lead to one or both codes being triggered. Check the lines and fittings to make sure there are no leaks before looking at the more expensive components. A good diesel technician in your area should be able to diagnose the condition and make the necessary repairs with relative ease.
Photo 4/6   |   001 DSLP 160800 TOPT Duramax EGT
Exhaust gas temperature plays a critical role in the life of a diesel truck’s turbocharger and engine. However, EGT is just one element of numerous factors that affect a diesel’s durability.
DuraMAX EGT
What is the safest “maximum EGT” for a Duramax LMM engine? I just retired, and my wife and I plan to travel a lot in the Rockies towing a gooseneck toy hauler trailer with a ’10 GMC Sierra 2500HD.
Steve H
-via the Internet
We’ve always subscribed to 1,200 degrees, measured at the exhaust manifold, as being at the edge of “safe” sustained exhaust gas temperature. When we asked Gary Arvan, GM’s Duramax chief engineer, about EGT, he told us diesel-engine durability cannot be predicted with a single limit such as temperature.
“There are many components to consider, and each is affected by numerous factors, such as pressure, temperature, rate of pressure rise, and so on,” Gary says. “That being said, 1,364 degrees is the peak temperature used [by GM] for both the LMM and LML engines with all other factors included in the production calibration.” Gary also made sure to mention that any “calibration changes” violate GM warranty and following a 1,364-degree guideline is “not sufficient to ensure durability.”
Photo 5/6   |   002 DSLP 160800 TOPT Swap
Photo 6/6   |   002A DSLP 160800 TOPT Swap
Swapping engines in same-brand trucks of different generations presents some big challenges beyond solving the basic electrical and plumbing concerns. There are also legal issues to consider, such as titles and licensing.
Engine Switching
I have an ’02 Dodge Ram 3500 longbed 4x4, and salt is starting to eat away at the body. I like the simplicity of the mechanical engine minus the injection pump but don't like not having a crew cab option in this generation of trucks. Rather than fixing or replacing my truck’s body with a rust-free one, can I use an ’03-or-newer body, keep its interior, and make the gauges and everything work with the VP44 engine?
Laurence in Pennsylvania
-via email
With enough time, talent, and money, you can do just about anything you want when it comes to vehicle modifications. Your ’02’s engine and transmission should bolt up easily in the ’03 chassis. Getting all the gauges and electrical bugs worked out will require a lot of work from what our sources tell us. But that should be the least of your concerns. The state and EPA will take considerable issue with your plans: It’s against the law (with a $2,500 penalty) to put an older engine in a newer, emissions-controlled vehicle, per the EPA's policy regarding "engine switching" under the provisions of Mobile Source Enforcement Memorandum No. lA (Attachment 1).
Then there’s the title. Vehicles are titled using the VIN of the body. In most counties of Pennsylvania, your “custom Dodge Ram” would have to pass emissions testing as an ’03 (or whatever year body you use) before being licensed. Trying to get the VP44 to duplicate the common-rail rig’s emissions isn’t going to happen.
Placing an ’03-and-up Crew Cab body on your ’02 rolling chassis isn’t going to be easy, either, according to some of our body shop contacts. The newer model’s wheelbase is apparently 3 to 6 inches longer, depending on cab/bed configuration. That means you’d have to fabricate all new body mounts and do frame and/or body modifications to make the swap work. And you will still be left with the same title and electrical challenges as putting the ’02 engine in the ’03 body.
Our suggestion: Do an Internet search for a rust-free, replacement ’02 body in the Southwest, or embrace the common-rail era and buy a newer Crew Cab that has the interior spaciousness you long for—without all the legal baggage

POPULAR TRUCKS

Subscribe Today and Save up to 83%!

Subscribe Truck Trend Magazine

Subscribe to:

Truck Trend
Magazine

PRINT DIGITAL
Subscribe Diesel Power Magazine

Subscribe to:

Diesel Power
Magazine

PRINT DIGITAL
Subscribe Truckin Magazine

Subscribe to:

Truckin
Magazine

PRINT DIGITAL
SUBSCRIBE TO A MAGAZINE
CLOSE X
BUYER'S GUIDE
SEE THE ALL NEW
NEWS, REVIEWS & SPECS