P0171 on RAM: How to Diagnose & Fix
System Too Lean (Bank 1)
1 RAM model · 1 documented issue · 1 critical · $150-$600 repair
P0171 on RAM by model: symptoms, diagnosis and fix
On Magnum-engine Rams the intake manifold has a stamped-steel plenum pan sealed to the aluminum manifold by a one-piece gasket. Because steel and aluminum expand at different rates, the gasket tears over time and lets engine oil from the lifter valley get drawn into the intake plenum and burned. Virtually every high-mileage 3.9/5.2/5.9 Magnum develops this. Burned oil fouls the oxygen sensors, causes detonation (pinging), and can destroy the catalytic converters if ignored.
Common Symptoms
- Excessive oil consumption with no external leak
- Sudden loss of fuel economy
- Pinging/detonation under load
- Rough running and low power
- Blue smoke / oil pooled in bottom of intake plenum
- Fouled spark plugs and O2 sensors
How to Fix
Remove the intake, discard the OE stamped plenum pan and install an aftermarket billet/thicker steel plenum repair plate with a new gasket (commonly sold as a 'plenum repair plate kit', e.g. the Mancini Racing kit for 5.2L/5.9L Magnum V8s), or install a Mopar/Fel-Pro intake/plenum gasket set matched to your Magnum engine. Inspect and replace fouled O2 sensors afterward. DIY parts run roughly $60-$180 (gasket/plate kit); shop labor adds the rest.
What you need to fix it
Only diagnosis- and fitment-reviewed repair parts are linked here.
- Hughes Engines HUG 7720FEL V8 Magnum plenum repair kit
1992-2003 Dodge/Jeep 5.2L and 5.9L Magnum V8 only; includes aluminum plate, premium Fel-Pro gaskets, bolts and bypass hose. Not for the 3.9L V6.
- Hughes Engines HUG 7725 V6 Magnum plenum repair kit
1992-2005 3.9L Magnum V6 only; confirm the 1994-2001 Ram 1500 engine before purchase.
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Sources for this issue (3)
P0171 code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does P0171 mean on a RAM?
P0171 stands for "System Too Lean (Bank 1)." This code means the engine's computer has detected that the air-fuel mixture on Bank 1 (the side of the engine with cylinder #1) is running too lean — meaning there is too much air relative to fuel. The computer watches the oxygen sensors and has had to add a large amount of extra fuel (long-term fuel trim) to try to compensate, but it has hit its correction limit. A lean condition can cause rough idle, hesitation, reduced power, and over time can run the engine hotter than normal. It usually points to either unmetered air leaking into the engine or not enough fuel being delivered. On RAM it is documented across 1 model: 1500.
What are the most common causes of P0171?
The most common causes of P0171 are: Vacuum or intake air leak (cracked hose, gasket, or PCV system), Dirty or failing mass airflow (MAF) sensor, Weak fuel pump or restricted fuel filter, Clogged or dirty fuel injectors, Faulty or aged upstream oxygen sensor, Leaking intake manifold gasket, Low fuel pressure or failing fuel pressure regulator, Exhaust leak ahead of the oxygen sensor. The specific cause varies by vehicle.
How much does it cost to fix P0171 on a RAM?
Published repair estimates on RAM range from $150 to $600 depending on the model and root cause. If an issue mentions a recall or campaign, check your VIN with the manufacturer or NHTSA and confirm eligibility and coverage with a dealer.
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Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.