What Does P1085 Mean?
The ECM has detected a lean fuel mixture condition based on feedback from the upstream oxygen sensor on Bank 2. The air-fuel ratio is consistently leaner than optimal on the second cylinder bank.
Common Causes
35%
Vacuum leak specific to Bank 2 intake
25%
Faulty fuel injector(s) on Bank 2 cylinders
20%
Exhaust leak before Bank 2 upstream oxygen sensor
12%
Faulty Bank 2 Sensor 1 oxygen sensor
8%
Fuel pressure issue or restriction in Bank 2 fuel rail
Diagnostic Steps
1
Step 1: Check for vacuum leaks specifically on Bank 2 side of engine
2
Step 2: Monitor fuel trim values separately for Bank 2 (STFT and LTFT)
3
Step 3: Inspect Bank 2 exhaust manifold and connections for leaks
4
Step 4: Compare fuel injector pulse width between Bank 1 and Bank 2
5
Step 5: Test Bank 2 upstream oxygen sensor response and voltage switching
Estimated Repair Cost
$150 - $800
Parts + labor, varies by vehicle and location
The ECM has detected a lean fuel mixture condition based on feedback from the upstream oxygen sensor on Bank 2. The air-fuel ratio is consistently leaner than optimal on the second cylinder bank.
The most common cause of P1085 (Fuel Control Mixture Lean (Bank 2 Sensor 1)) is: Vacuum leak specific to Bank 2 intake
Typical repair costs for P1085 range from $150 to $800, depending on the vehicle, location, and whether you do it yourself or go to a shop.
May cause rough idle, hesitation, and poor acceleration. Safe to drive short distances but repair promptly to prevent catalyst damage.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P1085 to identify the root cause.
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Quick Info
Category
Powertrain
System
Fuel System and Air Intake (Bank 2)
Difficulty
Type
Manufacturer
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