GM Atlas Vortec 3.7L LLR: Specs, Engine Codes, Controllers & Maintenance
Engine Information · GM · Atlas · revised five-cylinder
Atlas Vortec 3.7L LLR
The 3.7L LLR brings 242 hp to GM’s midsize pickups and H3. It retains the Atlas five-cylinder character, with port injection and exhaust cam phasing; the production-year controller split matters when selecting replacement electronics.
Engine construction
| Specification | Details |
|---|---|
| Capacity / layout | 3.7L · inline-five |
| Construction | Aluminum block and head |
| Valve gear | DOHC · 20 valves · exhaust cam phasing |
| Fuel / induction | Sequential port injection · naturally aspirated |
| Timing drive | Chain |
| Bore × stroke / compression | 95.5 × 102 mm · 10.0:1 |
Codes & output
| RPO / version | Power / torque | Key difference |
|---|---|---|
| LLR | 242 hp / 242 lb-ft | Canyon / Colorado rating |
SAE horsepower; torque in lb-ft. Ratings are for the stated application and fuel, rather than every vehicle with this RPO.
Vehicles & model years
| Brand | Model | Model years | Platform / chassis | Engine RPO |
|---|---|---|---|---|
| GMC / Chevrolet | Canyon / Colorado | 2007–2012 | GMT355 | LLR |
| Hummer | H3 / H3T | 2007–2010; H3T 2009–2010 | GMT345 | LLR |
U.S. and Canadian applications within the 2005–2026 matrix scope. Engine availability depends on trim, build date and emissions certification.
Engine controllers
| Application / revision | ECM or PCM | Identification & function |
|---|---|---|
| 2007 pickup | GM P12 PCM | Confirm hardware and calibration; integrated powertrain control |
| 2008+ pickup | GM E67 ECM | Separate engine/transmission electronics; confirm H3-specific application by VIN |
Identify the module from its service number, operating-system ID and VIN. The ECM/PCM and transmission controller have separate calibrations on many applications; a matching RPO alone does not make a replacement module plug-and-play.
Common issues & maintenance
- Cam timing / oil controlP0014/P0017 or a rough idle can involve the cam-actuator solenoid and its screens. GM also calls for crankshaft end-play checks when ordinary diagnosis does not explain the condition; do not assume a chain is at fault from the code alone.
- Ignition and air leaksCoils, worn plugs and intake leaks can cause rough running. Use cylinder misfire counts and fuel trims to separate ignition faults from mechanical compression loss.
- Oil level and coolingLow oil can compromise cam-phaser operation. Repair coolant and oil leaks promptly and keep the cooling system in good condition.
Keep it healthy. Use the correct oil grade and keep the level full; cam phasing depends on oil delivery. Follow plug, coolant and filter schedules. Persistent misfires need compression and leak-down tests before repeated parts replacement.
References & technical sources
| Source | Reference |
|---|---|
| GM applications & RPO diagnostic matrices | View source |
| EFILive GM gasoline controller families | View source |
| EFILive production controller database | View source |
| GM Atlas cam-actuator diagnostic bulletin | View source |
| GMC 2007 Canyon factory specifications | View source |
