Fuel System Monitor

OBD System Description - Fuel System Monitor

Fuel Trim Lean/Rich

DTC Description / Detecting Condition / Confirmation Procedure
P0171 (Fuel Trim B1 Lean) refer to DTC P0171: Fuel Trim System Lean. P0171
P0172 (Fuel Trim B1 Rich) refer to DTC P0172: Fuel Trim System Rich. P0172
P2187 (Fuel Trim B1 ICO Lean) refer to DTC P2187: Fuel Trim System Lean at Idle. P2187
P2188 (Fuel Trim B1 ICO Rich) refer to DTC P2188: Fuel Trim System Rich at Idle. P2188

Monitor Strategy Description
Fuel Trim Limits Exceeded (P0171, P0172)
A - The average of short term fuel trim values
AND
B - The average of adaptive index multiplier values
Fuel Trim Idle Condition Option Limits Exceeded (P2187, P2188)
A - The average of short term fuel trim values
AND
B - The average of adaptive index multiplier values

Malfunction Criteria
Fuel Trim Limits Exceeded (P0171, P0172)
A
Rich Limit Average > 1.0601 multiplier
Lean Limit Average < 0.94 multiplier
B
Rich Limit Average > 0.8 multiplier
Lean Limit Average < 1.25 multiplier
Fuel Trim Idle Condition Option Limits Exceeded (P2187, P2188)
A
Rich Limit Average > 1.5 multiplier
Lean Limit Average < 0.8 multiplier
B
Rich Limit Average > 0.78 multiplier
Lean Limit Average < 1.27 multiplier

Enable Conditions
Engine Speed = 700 rpm
AND Engine Speed = 6,000 rpm
AND Engine coolant temperature = 70 degrees C
AND Engine coolant temperature = 115 degrees C
AND Intake Air Temperature = -40 degrees C
AND Intake Air Temperature = 120 degrees C
AND Throttle Position = 0%
AND Throttle Position = 95.0012%
AND Engine Load = 25 kPa
AND Engine Load = 99.6992 kPa
AND Intake Air Flow = 1.5 g/s
AND Intake Air Flow = 45 g/s
AND Barometric Pressure = 72 kPa
AND Vehicle Speed = 140 kph
AND System Voltage = 11 V
AND Closed Loop Active = TRUE
AND BLM learn Allowed = TRUE
AND Other diagnostic fault active = FALSE
AND Other diagnostic fault during this key cycle = FALSE

Time required
Fuel Trim Limits Exceeded (P0171, P0172.
Time Length and Frequency:
6 test failures within a 10 test samples at loop time of 125 ms.
Failure Time:
Continuous monitoring.
Fuel Trim Idle Condition Option Limits Exceeded (P2187, P2188.
Time Length and Frequency:
3 test failures within a 10 test samples at loop time of 125 ms.
Failure Time:
Continuous monitoring.