2017+ CHEVY SILVERADO / GMC SIERRA HD · 6.6L DURAMAX L5P
L5P Duramax repair in Tucson: weak points & fixes.
The L5P is the strongest Duramax yet. GM fixed the LML’s fuel pump problem with a Denso pump and a factory lift pump, so most issues today are emissions sensors, soot and maintenance. Here’s what we see and how we fix it at your location.
- 445–470 hp910–975 lb-ft stock
- Denso HP4factory lift pump
- Allison 6- or 10-speedautomatic
- We come to youTucson & nearby
Jump to a system
KNOW YOUR TRUCK
Which L5P? It changes the parts.
The L5P has had two body styles, two transmissions and a power bump. Your year tells us which parts to bring.
Allison 1000 6-speed
- 445 hp / 910 lb-ft
- Older body style
- Banks Ram-Air and Derringer for 2017–2019
- PPE pans made for 2017–2019
Allison 10L1000 10-speed
- 445 hp / 910 lb-ft through 2023
- 470 hp / 975 lb-ft from 2024 (new turbo and injectors)
- New body; different pans and diff cover
- Banks Ram-Air and Derringer for 2020–2023
POWER THROUGH THE YEARS
Where the L5P Duramax fits in Duramax history.
Peak factory pickup ratings by generation, horsepower and torque. Yours is highlighted. Tap any bar to see that generation.
- Horsepower
- Torque (lb-ft)
WEAK POINTS, SYSTEM BY SYSTEM
What fails on the L5P Duramax, and how we fix it.
Tap a system to see what fails, what you’ll notice and how we fix it. Common = we see it often. Towing / tuned = shows up with heavy loads or added power. High miles = age and wear items.
DEF, DPF & EGR
DEF system and level readingsCommon
You’ll notice: a “Service DEF” message, wrong DEF level, a countdown to reduced speed.
Why: DEF sensors, heaters and level readings fail on some trucks, especially 2020 and newer.
Our fix: We diagnose the DEF system and replace the failed part, keeping it legal.
NOx and exhaust sensorsCommon
You’ll notice: check engine light, derate, failed regens.
Why: Sensors in the exhaust fail with heat and age.
Our fix: We test each sensor and replace the failed one.
DPF and EGR sootHigh miles
You’ll notice: frequent regens, low power, EGR codes.
Why: Short trips and idling load the DPF and EGR with soot.
Our fix: We clean or replace emissions parts the legal way.
Intake & turbo
Soot on the MAP sensorCommon
You’ll notice: low power, boost codes, a rough feel.
Why: EGR soot builds up in the intake and on the MAP sensor.
Our fix: We clean the intake and sensor; a Banks MAP sensor relocation kit keeps it cleaner.
Fuel system
Water in fuel and plugged filtersCommon
You’ll notice: a water-in-fuel light, low power, hard starts.
Why: The HP4 pump and injectors need clean, dry fuel.
Our fix: We drain water, change filters on time and check fuel pressure.
Allison 6- and 10-speed
Harsh shifts or limp modeTowing / tuned
You’ll notice: flare, harsh shifts, a transmission message.
Why: Old fluid and heat wear out clutches, and software updates can be needed.
Our fix: We service it, check for updates and diagnose the codes.
Front end & steering
Loose steeringHigh miles
You’ll notice: wandering, play in the wheel, uneven tire wear.
Why: The independent front end wears tie rods and ball joints on these heavy trucks.
Our fix: We rebuild the front end with heavy-duty parts and set the alignment.
RELIABILITY UPGRADES
Bulletproof it in the right order.
If you plan to keep your L5P, these are the upgrades we recommend, in the order that protects it best.
- Fuel filters on timeClean, dry fuel protects the HP4 pump and injectors.Call nowRequest a quote
- MAP sensor relocationA Banks kit keeps the MAP sensor out of the soot.Call nowRequest a quote
- Deep transmission panA PPE pan adds about a gallon of fluid for the Allison.Call nowRequest a quote
- Deep oil panA PPE pan adds 2 quarts and drains completely at oil changes.Call nowRequest a quote
- Recalls checkedWe check for open GM recalls and updates at every visit.Call nowRequest a quote
MAINTENANCE SCHEDULE
L5P Duramax service intervals.
These are GM’s factory intervals from the owner’s manual schedule. The factory “severe” column covers towing, dusty roads, short trips and long idling, which describes most working trucks in Southern Arizona. Our recommendation follows the severe schedule, with oil every 5,000 miles and fuel filters every 10,000.
| Service | Factory, normal use | Factory, severe use | Our recommendation |
|---|---|---|---|
| Engine oil & filter | 10,000 mi / 12 months or oil life monitor (maximum) | Sooner when towing or idling | Every 5,000 mi |
| Fuel filter & water separator | 22,500 mi / 2 years or dash message | Same | Every 10,000 mi |
| Engine air filter | 45,000 mi / 4 years or dash message | Check at every oil change | Check at every oil change |
| Coolant | 150,000 mi / 5 years first, then 50,000 mi | Same | 150,000 mi / 5 years first, then 50,000 mi |
| Allison 6-speed or 10-speed fluid & filters | 45,000 mi | Same | 45,000 mi |
| Transfer case fluid | 50,000 mi | Same | 50,000 mi |
| Front & rear axle fluid | Not set by the factory | Not set by the factory | No factory interval; we inspect it at every service |
Always go by your owner’s manual for your exact truck. Factory figures are maximums, and the dash service reminder comes first when it shows sooner.
WANT MORE POWER?
L5P Duramax performance upgrades.
Staged builds, lift pumps, transmission, exhaust and suspension upgrades for the L5P Duramax.
BUYING A L5P DURAMAX?
Get it inspected before you buy.
Our Diesel Pre-Purchase Inspection checks the engine, fuel system, transmission and front end, and looks for signs of past problems. We meet you at the seller.
How mobile service worksTell us your truck and where it is, we diagnose on site, you approve a written estimate, and we fix it where it sits.
See how it works →PLAIN-ENGLISH GLOSSARY
L5P Duramax terms, explained.
- L5P
- The 6.6L Duramax used from 2017 to today.
- HP4
- The Denso high-pressure fuel pump on the L5P.
- 10L1000
- The Allison 10-speed automatic used from 2020.
- DEF
- Diesel exhaust fluid. Sprayed into the exhaust to cut NOx.
- MAP sensor
- Measures boost pressure in the intake.
- DPF
- Diesel particulate filter. Traps soot in the exhaust.
Name-brand partsWe install proven brands like Banks, PPE, aFe and Bilstein.
See all the brands we install →OWNER QUESTIONS
L5P Duramax questions, answered.
Is the L5P reliable?
Yes. GM replaced the LML’s CP4 with a Denso HP4 pump and added a factory lift pump. Most problems now are emissions sensors and soot.
My truck says “Service DEF.” What now?
Don’t ignore it; the truck will slow itself down. Call us and we’ll find the failed sensor, heater or pump.
Do you work on newer trucks still under warranty?
Yes, for maintenance and out-of-warranty repairs. For warranty items, we’ll tell you when the dealer should handle it.
Why don’t you list prices for these repairs?
Every truck is different. Mileage, past repairs and how it’s used all change the parts and labor. Call us at 520-990-1033 and we’ll give you a straight quote.
What warranty do repairs have?
Repair labor is backed for 1 year or 12,000 miles, and new parts carry their manufacturer’s warranty. Warranty details →
LET’S TALK ABOUT YOUR TRUCK
Call, text or request a quote.
Tell us your year, mileage and what you want done. We’ll recommend the right repair, quote it and come to you.