P0172 Issue
#1
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Year: 2000
Model: Cherokee
Engine: 4.0L I6
P0172 Issue
Question on an engine control issue:
I've been consistently getting a P0172 code (Bank 1/1 Running Rich) for a few months now. That is the only code present. Other symptoms are that it runs pretty rough at cold idle, but is fine at running temp.
According to Freeze-Frame data (idle conditions) the Short Term Fuel Trim was at -3.1%, and the Long Term Fuel Trim at -32.8%.
I replaced the MAP sensor and cleaned the throttle body, but the code still shows up. All fuel injectors were recently replaced, and I haven't found any vacuum leaks, so I'm a bit lost as to what is causing the rich condition. Any ideas?
Thanks!
I've been consistently getting a P0172 code (Bank 1/1 Running Rich) for a few months now. That is the only code present. Other symptoms are that it runs pretty rough at cold idle, but is fine at running temp.
According to Freeze-Frame data (idle conditions) the Short Term Fuel Trim was at -3.1%, and the Long Term Fuel Trim at -32.8%.
I replaced the MAP sensor and cleaned the throttle body, but the code still shows up. All fuel injectors were recently replaced, and I haven't found any vacuum leaks, so I'm a bit lost as to what is causing the rich condition. Any ideas?
Thanks!
#4
CF Veteran
Probably un-metered air intake (leak) that self resolves as things warm up and expand.
A cold vehicle smoke test is probably the most efficient way to find the source. You could continue to poke around with something like propane to try and detect a leak, but you'll probably only be able to catch it when the vehicle is dead cold.
This might be one of those times when letting a shop do the smoke test pays off, just to help reduce the amount of guess work, so that you can get to fixing it.
It could also be the excuse you've been waiting for to buy (or build) your own smoke tester.
A cold vehicle smoke test is probably the most efficient way to find the source. You could continue to poke around with something like propane to try and detect a leak, but you'll probably only be able to catch it when the vehicle is dead cold.
This might be one of those times when letting a shop do the smoke test pays off, just to help reduce the amount of guess work, so that you can get to fixing it.
It could also be the excuse you've been waiting for to buy (or build) your own smoke tester.
#6
CF Veteran
If by cat/O2 sensor you mean the downstream sensor (the one furthest from the motor), then no, probably not. It is used for emissions monitoring, but it is not used by the ECM to make air fuel adjustments.
If instead you mean the upstream sensor, nearest the motor, then yes possibly. If it were reading (or reporting) high remaining oxygen in the exhaust then the long term fuel trim will keep adjusting upwards to compensate.
Do your fuel trims change or start to go down once the vehicle is hot?
If instead you mean the upstream sensor, nearest the motor, then yes possibly. If it were reading (or reporting) high remaining oxygen in the exhaust then the long term fuel trim will keep adjusting upwards to compensate.
Do your fuel trims change or start to go down once the vehicle is hot?
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#9
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I haven't been able to look at fuel trims in real time, but I would assume the Long Term drops after startup. If I can get my hands on a better scan tool, I'll see how it acts when it's cold.
#10
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Year: 1999
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Engine: 4.0
Diagnostic data.
P0172-1/1 FUEL SYSTEM RICH
WhenMonitored: With the engine running in closed loop mode, the ambient/battery temperatureabove 20 deg. F and altitude below 8000 ft.
SetCondition: If the PCM multiplies short term compensation by long term adaptive and the result is below a certain value for two trips, a freeze frame isstored, the MIL illuminates and a trouble code is stored.
POSSIBLE CAUSES
INTERMITTENT CONDITION
RESTRICTED FUEL SUPPLY LINE
FUEL PUMP INLET STRAINER PLUGGED
FUEL PUMP MODULE
O2 SENSOR HEATER OPERATION
O2 SENSOR
EVAP SYSTEM OPERATION
O2 SENSOR SIGNAL CIRCUIT SHORTED TO VOLTAGE
O2 SENSOR SIGNAL CIRCUIT OPEN
TPS VOLTAGE GREATER THAN 0.92 VOLTS WITH THROTTLE CLOSED
TP SENSOR SWEEP
MAP SENSOR OPERATION
ECT SENSOR OPERATION
ENGINE MECHANICAL PROBLEM
FUEL FILTER/PRESSURE REGULATOR (HIGH)
PCM
P0172-1/1 FUEL SYSTEM RICH
WhenMonitored: With the engine running in closed loop mode, the ambient/battery temperatureabove 20 deg. F and altitude below 8000 ft.
SetCondition: If the PCM multiplies short term compensation by long term adaptive and the result is below a certain value for two trips, a freeze frame isstored, the MIL illuminates and a trouble code is stored.
POSSIBLE CAUSES
INTERMITTENT CONDITION
RESTRICTED FUEL SUPPLY LINE
FUEL PUMP INLET STRAINER PLUGGED
FUEL PUMP MODULE
O2 SENSOR HEATER OPERATION
O2 SENSOR
EVAP SYSTEM OPERATION
O2 SENSOR SIGNAL CIRCUIT SHORTED TO VOLTAGE
O2 SENSOR SIGNAL CIRCUIT OPEN
TPS VOLTAGE GREATER THAN 0.92 VOLTS WITH THROTTLE CLOSED
TP SENSOR SWEEP
MAP SENSOR OPERATION
ECT SENSOR OPERATION
ENGINE MECHANICAL PROBLEM
FUEL FILTER/PRESSURE REGULATOR (HIGH)
PCM
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