Cel - P0171
Sep 22, 2007, 07:21 AM
#1
Cel - P0171
ok so i had a piggyback and it was throwing this code. I assumed it was the piggy so i removed it. Apparently it wasn't. The code is
P0171 - System To Lean (Bank 1)
i just replaced the plugs, wires, and the 1st O2 sensor.
i'm thinking it could be the coilpacks, or maybe the second O2 sensor.
anyone got any idea?
P0171 - System To Lean (Bank 1)
i just replaced the plugs, wires, and the 1st O2 sensor.
i'm thinking it could be the coilpacks, or maybe the second O2 sensor.
anyone got any idea?
Sep 22, 2007, 08:11 AM
#3
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AllData description: (if any of this helps, let me know and I can try and get you the pictures associated with this. Most of the pictures just show a scan tool being plugged in, but there's an occasional wiring pinout, etc.)
DTC P0171: System too Lean
System too Lean Circuit
Refer to, DTC P0201 - P0204 Injector Circuit Malfunction.
CIRCUIT OPERATION
Refer to, DTC P0201 - P0204 Injector Circuit Malfunction.
TECHNICAL DESCRIPTION
If a malfunction occurs in the fuel system, the fuel trim value becomes too large.
The ECM or PCM checks whether the fuel trim value is within a specified range.
DTC SET CONDITIONS
Check Conditions
Engine coolant temperature is lower than approximately 100 °C (212 °F) when the engine is started.
Intake air temperature is lower than 60 °C (140 °F) when the engine is started.
Under the closed loop air/fuel ratio control.
Engine coolant temperature is higher than 77 °C (171 °F) .
Volume air flow sensor output frequency is 81 Hz or more.
Judgment Criteria
Long-term fuel trim has continued to be higher than +12.5 percent for 5 seconds . or
Short-term fuel trim has continued to be higher than +10.0 percent for 5 seconds .
Check Conditions
Engine coolant temperature is lower than approximately 100 °C (212 °F) when the engine is started.
Intake air temperature is lower than 60 °C (140 °F) when the engine is started.
Under the closed loop air/fuel ratio control.
Engine coolant temperature is higher than 77 °C (171 °F) .
Volume air flow sensor output frequency is 81 Hz or less.
Judgment Criteria
Long-term fuel trim has continued to be higher than +12.5 percent for 5 seconds . or
Short-term fuel trim has continued to be higher than +15 percent for 5 seconds .
Check Conditions
Engine coolant temperature is higher than approximately 100 °C (212 °F) when the engine is started.
Intake air temperature is higher than 60 °C (140 °F) when the engine is started.
Under the closed loop air/fuel ratio control.
Engine coolant temperature is higher than 77 °C (171 °F) .
Volume air flow sensor output frequency is 81 Hz or more.
Judgment Criteria
Long-term fuel trim has continued to be higher than +12.5 percent for 5 seconds . or
Short-term fuel trim has continued to be higher than +20.0 percent for 5 seconds .
Check Conditions
Engine coolant temperature is higher than approximately 100 °C (212 °F) when the engine is started.
Intake air temperature is higher than 60 °C (140 °F) when the engine is started.
Under the closed loop air/fuel ratio control.
Engine coolant temperature is higher than 77 °C (171 °F) .
Volume air flow sensor output frequency is 81 Hz or less.
Judgment Criteria
Long-term fuel trim has continued to be higher than +12.5 percent for 5 seconds . or
Short-term fuel trim has continued to be higher than +25.0 percent for 5 seconds .
Check Conditions
Engine coolant temperature is higher than 77 °C (171 °F) .
Under the closed loop air/fuel ratio control.
Judgment Criteria
Long-term fuel trim has continued to be +12.5 percent for 5 seconds . or
Short-term fuel trim has continued to be +25.0 percent for 5 seconds .
TROUBLESHOOTING HINTS (The most likely causes for this code to be set are
Volume air flow sensor failed.
Injector failed.
Incorrect fuel pressure.
Air drawn in from gaps in gasket, seals, etc.
Heated oxygen sensor failed.
Engine coolant temperature sensor failed.
Intake air temperature sensor failed.
Barometric pressure sensor failed.
Use of incorrect or contaminated fuel.
ECU failed.
PCM failed.
DIAGNOSIS
Required Special Tool:
MB991502: Scan Tool (MUT-II)
STEP 1. Check for exhaust leaks.
Q: Are there any abnormalities?
YES: Go to Step 2.
NO: Repair it. Then go to Step 14.
STEP 2. Check for intake system vacuum leaks.
Q: Are there any abnormalities?
YES: Go to Step 3.
NO: Repair it. Then go to Step 14.
STEP 3. Using scan tool MB991502, check data list item 12: Volume Air Flow Sensor.
CAUTION: To prevent damage to scan tool MB991502, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991502.
Connect scan tool MB991502 to the data link connector.
Start the engine and run at idle.
Set scan tool MB991502 to the data reading mode for item 12, Volume Air Flow Sensor.
Warm up the engine to normal operating temperature: 80 °C to 95 °C (176 °F to 203 °F) .
When idling, between 20 and 46 Hz (between 1.3 and 3.3 gm/s ).
When 2,500 r/min , between 70 and 110 Hz (between 6.6 and 10.2 gm/s ).
Turn the ignition switch to the "LOCK" (OFF) position. Q: Is the sensor operating properly? YES : Go to Step 4. NO : Refer to, DTC P0101 - Volume Air Flow Circuit Range/Performance Problem, DTC P0102 - Volume Air Flow Circuit Low Input.
STEP 4. Using scan tool MB991502, check data list item 13: Intake Air Temperature Sensor.
Turn the ignition switch to the "ON" position.
Set scan tool MB991502 to the data reading mode for item 13, Intake Air Temperature Sensor.
The intake air temperature and temperature shown with the scan tool should approximately match.
Turn the ignition switch to the "LOCK" (OFF) position. Q: Is the sensor operating properly? YES : Go to Step 5. NO : Refer to, DTC P0111 - Intake Air Temperature Circuit Range/Performance Problem, DTC P0112 - Intake Air Temperature Circuit Low Input, DTC P0113- Intake Air Temperature Circuit High input.
STEP 5. Using scan tool MB991502, check data list item 21: Engine Coolant Temperature Sensor.
Turn the ignition switch to the "ON" position.
Set scan tool MB991502 to the data reading mode for item 21, Engine Coolant Temperature Sensor.
The engine coolant temperature and temperature shown with the scan tool should approximately match.
Turn the ignition switch to the "LOCK" (OFF) position. Q: Is the sensor operating properly? YES: Go to Step 6. NO: Refer to, DTC P0116 - Engine Coolant Temperature Circuit Range/Performance Problem, DTC P0117 - Engine Coolant Temperature Circuit Low Input, DTC P0118 - Engine Coolant Temperature Circuit High Input.
STEP 6. Using scan tool MB991502, check data list item 25: Barometric Pressure Sensor.
Turn the ignition switch to the "ON" position.
Set scan tool MB991502 to the data reading mode for item 25, Barometric Pressure Sensor.
When altitude is 0 m (0 foot), 101 kPa (29.8 in.Hg) .
When altitude is 600 m (1,969 feet), 95 kPa (28.1 in.Hg) .
When altitude is 1,200 m (3,937 feet), 88 kPa (26.0 in.Hg) .
When altitude is 1,800 m (5,906 feet), 81 kPa (23.9 in.Hg) .
Turn the ignition switch to the "LOCK" (OFF) position. Q: Is the sensor operating properly? YES: Go to Step 7. NO: Refer to, DTC P0106 - Barometric Pressure Circuit Range/Performance Problem, DTC P0107 - Barometric Pressure Circuit Low Input, DTC P0108 - Barometric Pressure Circuit High Input.
STEP 7. Check connectors B-17, B-18, B-20, B-22 at injector for damage.
Q: Is the connector in good condition?
YES: Go to Step 8.
NO: Repair or replace it. Refer to Harness Connector Inspection. Then go to Step 14.
STEP 8. Check the injector.
Disconnect each injector connector.
Measure the resistance between injector side connector terminal No. 1 and No. 2. Standard value: 13-16 ohms [at 20 °C (68 °F)] Q: Is the resistance between 13 and 16 ohms [at 20 °C (68 °F)] ? YES: Go to Step 9. NO: Replace the injector. Then go to Step 14.
STEP 9. Check connector C-121 at ECM or connector C-120 at PCM for damage.
Q: Is the connector in good condition?
YES: Go to Step 10.
NO: Repair or replace it. Refer to Harness Connector Inspection. Then go to Step 14.
STEP 10. Check for harness damage between injector connector and ECM connector or PCM connector .
Check the harness wire between injector connector B-22 (terminal No. 2) and ECM connector C-121 (terminal No. 1) or PCM connector C-120 (terminal No. 1) when checking No. 1 cylinder.
Check the harness wire between injector connector B-20 (terminal No. 2) and ECM connector C-121 (terminal No.14) or PCM connector C-120 (terminal No. 9) when checking No. 2 cylinder.
Check the harness wire between injector connector B-18 (terminal No. 2) and ECM connector C-121 (terminal No. 2) or PCM connector C-120 (terminal No. 24) when checking No. 3 cylinder.
Check the harness wire between injector connector B-17 (terminal No. 2) and ECM connector C-121 (terminal No.15) or PCM connector C-120 (terminal No. 2) when checking No. 4 cylinder. Q: Is the harness wire in good condition? YES: Go to Step 11. NO: Repair it. Then go to Step 14.
STEP 11. Check the fuel pressure.
Refer to On-vehicle Service - Fuel Pressure Test.
Q: Is the fuel pressure normal?
YES: Go to Step 12.
NO: Repair or replace it. Then go to Step 14.
STEP 12. Check for entry of foreign matter (water, kerosene, etc.) into fuel.
Q: Are there any abnormalities?
YES: Go to Step 13.
NO: Replace the fuel. Then go to Step 14.
STEP 13. Replace the injector.
Replace the injector.
Carry out a test drive with the drive cycle pattern. Refer to Trouble Code Diagnosis- OBD-II Drive Cycle - Procedure 2 - Fuel Trim Monitor.
Check the diagnostic trouble code (DTC). Q: Is DTC P0171 set? YES: Replace the ECM or PCM. Then go to Step 14. NO: The procedure is complete.
STEP 14. Perform the OBD-II drive cycle.
Carry out a test drive with the drive cycle pattern. Refer to Trouble Code Diagnosis- OBD-II Drive Cycle - Procedure 2 - Fuel Trim Monitor.
Check the diagnostic trouble code (DTC). Q: Is DTC P0171 set? YES: Repeat the troubleshooting. NO: The procedure is complete.
DTC P0171: System too Lean
System too Lean Circuit
Refer to, DTC P0201 - P0204 Injector Circuit Malfunction.
CIRCUIT OPERATION
Refer to, DTC P0201 - P0204 Injector Circuit Malfunction.
TECHNICAL DESCRIPTION
If a malfunction occurs in the fuel system, the fuel trim value becomes too large.
The ECM or PCM checks whether the fuel trim value is within a specified range.
DTC SET CONDITIONS
Check Conditions
Engine coolant temperature is lower than approximately 100 °C (212 °F) when the engine is started.
Intake air temperature is lower than 60 °C (140 °F) when the engine is started.
Under the closed loop air/fuel ratio control.
Engine coolant temperature is higher than 77 °C (171 °F) .
Volume air flow sensor output frequency is 81 Hz or more.
Judgment Criteria
Long-term fuel trim has continued to be higher than +12.5 percent for 5 seconds . or
Short-term fuel trim has continued to be higher than +10.0 percent for 5 seconds .
Check Conditions
Engine coolant temperature is lower than approximately 100 °C (212 °F) when the engine is started.
Intake air temperature is lower than 60 °C (140 °F) when the engine is started.
Under the closed loop air/fuel ratio control.
Engine coolant temperature is higher than 77 °C (171 °F) .
Volume air flow sensor output frequency is 81 Hz or less.
Judgment Criteria
Long-term fuel trim has continued to be higher than +12.5 percent for 5 seconds . or
Short-term fuel trim has continued to be higher than +15 percent for 5 seconds .
Check Conditions
Engine coolant temperature is higher than approximately 100 °C (212 °F) when the engine is started.
Intake air temperature is higher than 60 °C (140 °F) when the engine is started.
Under the closed loop air/fuel ratio control.
Engine coolant temperature is higher than 77 °C (171 °F) .
Volume air flow sensor output frequency is 81 Hz or more.
Judgment Criteria
Long-term fuel trim has continued to be higher than +12.5 percent for 5 seconds . or
Short-term fuel trim has continued to be higher than +20.0 percent for 5 seconds .
Check Conditions
Engine coolant temperature is higher than approximately 100 °C (212 °F) when the engine is started.
Intake air temperature is higher than 60 °C (140 °F) when the engine is started.
Under the closed loop air/fuel ratio control.
Engine coolant temperature is higher than 77 °C (171 °F) .
Volume air flow sensor output frequency is 81 Hz or less.
Judgment Criteria
Long-term fuel trim has continued to be higher than +12.5 percent for 5 seconds . or
Short-term fuel trim has continued to be higher than +25.0 percent for 5 seconds .
Check Conditions
Engine coolant temperature is higher than 77 °C (171 °F) .
Under the closed loop air/fuel ratio control.
Judgment Criteria
Long-term fuel trim has continued to be +12.5 percent for 5 seconds . or
Short-term fuel trim has continued to be +25.0 percent for 5 seconds .
TROUBLESHOOTING HINTS (The most likely causes for this code to be set are
Volume air flow sensor failed.
Injector failed.
Incorrect fuel pressure.
Air drawn in from gaps in gasket, seals, etc.
Heated oxygen sensor failed.
Engine coolant temperature sensor failed.
Intake air temperature sensor failed.
Barometric pressure sensor failed.
Use of incorrect or contaminated fuel.
ECU failed.
PCM failed.
DIAGNOSIS
Required Special Tool:
MB991502: Scan Tool (MUT-II)
STEP 1. Check for exhaust leaks.
Q: Are there any abnormalities?
YES: Go to Step 2.
NO: Repair it. Then go to Step 14.
STEP 2. Check for intake system vacuum leaks.
Q: Are there any abnormalities?
YES: Go to Step 3.
NO: Repair it. Then go to Step 14.
STEP 3. Using scan tool MB991502, check data list item 12: Volume Air Flow Sensor.
CAUTION: To prevent damage to scan tool MB991502, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991502.
Connect scan tool MB991502 to the data link connector.
Start the engine and run at idle.
Set scan tool MB991502 to the data reading mode for item 12, Volume Air Flow Sensor.
Warm up the engine to normal operating temperature: 80 °C to 95 °C (176 °F to 203 °F) .
When idling, between 20 and 46 Hz (between 1.3 and 3.3 gm/s ).
When 2,500 r/min , between 70 and 110 Hz (between 6.6 and 10.2 gm/s ).
Turn the ignition switch to the "LOCK" (OFF) position. Q: Is the sensor operating properly? YES : Go to Step 4. NO : Refer to, DTC P0101 - Volume Air Flow Circuit Range/Performance Problem, DTC P0102 - Volume Air Flow Circuit Low Input.
STEP 4. Using scan tool MB991502, check data list item 13: Intake Air Temperature Sensor.
Turn the ignition switch to the "ON" position.
Set scan tool MB991502 to the data reading mode for item 13, Intake Air Temperature Sensor.
The intake air temperature and temperature shown with the scan tool should approximately match.
Turn the ignition switch to the "LOCK" (OFF) position. Q: Is the sensor operating properly? YES : Go to Step 5. NO : Refer to, DTC P0111 - Intake Air Temperature Circuit Range/Performance Problem, DTC P0112 - Intake Air Temperature Circuit Low Input, DTC P0113- Intake Air Temperature Circuit High input.
STEP 5. Using scan tool MB991502, check data list item 21: Engine Coolant Temperature Sensor.
Turn the ignition switch to the "ON" position.
Set scan tool MB991502 to the data reading mode for item 21, Engine Coolant Temperature Sensor.
The engine coolant temperature and temperature shown with the scan tool should approximately match.
Turn the ignition switch to the "LOCK" (OFF) position. Q: Is the sensor operating properly? YES: Go to Step 6. NO: Refer to, DTC P0116 - Engine Coolant Temperature Circuit Range/Performance Problem, DTC P0117 - Engine Coolant Temperature Circuit Low Input, DTC P0118 - Engine Coolant Temperature Circuit High Input.
STEP 6. Using scan tool MB991502, check data list item 25: Barometric Pressure Sensor.
Turn the ignition switch to the "ON" position.
Set scan tool MB991502 to the data reading mode for item 25, Barometric Pressure Sensor.
When altitude is 0 m (0 foot), 101 kPa (29.8 in.Hg) .
When altitude is 600 m (1,969 feet), 95 kPa (28.1 in.Hg) .
When altitude is 1,200 m (3,937 feet), 88 kPa (26.0 in.Hg) .
When altitude is 1,800 m (5,906 feet), 81 kPa (23.9 in.Hg) .
Turn the ignition switch to the "LOCK" (OFF) position. Q: Is the sensor operating properly? YES: Go to Step 7. NO: Refer to, DTC P0106 - Barometric Pressure Circuit Range/Performance Problem, DTC P0107 - Barometric Pressure Circuit Low Input, DTC P0108 - Barometric Pressure Circuit High Input.
STEP 7. Check connectors B-17, B-18, B-20, B-22 at injector for damage.
Q: Is the connector in good condition?
YES: Go to Step 8.
NO: Repair or replace it. Refer to Harness Connector Inspection. Then go to Step 14.
STEP 8. Check the injector.
Disconnect each injector connector.
Measure the resistance between injector side connector terminal No. 1 and No. 2. Standard value: 13-16 ohms [at 20 °C (68 °F)] Q: Is the resistance between 13 and 16 ohms [at 20 °C (68 °F)] ? YES: Go to Step 9. NO: Replace the injector. Then go to Step 14.
STEP 9. Check connector C-121 at ECM or connector C-120 at PCM for damage.
Q: Is the connector in good condition?
YES: Go to Step 10.
NO: Repair or replace it. Refer to Harness Connector Inspection. Then go to Step 14.
STEP 10. Check for harness damage between injector connector and ECM connector or PCM connector .
Check the harness wire between injector connector B-22 (terminal No. 2) and ECM connector C-121 (terminal No. 1) or PCM connector C-120 (terminal No. 1) when checking No. 1 cylinder.
Check the harness wire between injector connector B-20 (terminal No. 2) and ECM connector C-121 (terminal No.14) or PCM connector C-120 (terminal No. 9) when checking No. 2 cylinder.
Check the harness wire between injector connector B-18 (terminal No. 2) and ECM connector C-121 (terminal No. 2) or PCM connector C-120 (terminal No. 24) when checking No. 3 cylinder.
Check the harness wire between injector connector B-17 (terminal No. 2) and ECM connector C-121 (terminal No.15) or PCM connector C-120 (terminal No. 2) when checking No. 4 cylinder. Q: Is the harness wire in good condition? YES: Go to Step 11. NO: Repair it. Then go to Step 14.
STEP 11. Check the fuel pressure.
Refer to On-vehicle Service - Fuel Pressure Test.
Q: Is the fuel pressure normal?
YES: Go to Step 12.
NO: Repair or replace it. Then go to Step 14.
STEP 12. Check for entry of foreign matter (water, kerosene, etc.) into fuel.
Q: Are there any abnormalities?
YES: Go to Step 13.
NO: Replace the fuel. Then go to Step 14.
STEP 13. Replace the injector.
Replace the injector.
Carry out a test drive with the drive cycle pattern. Refer to Trouble Code Diagnosis- OBD-II Drive Cycle - Procedure 2 - Fuel Trim Monitor.
Check the diagnostic trouble code (DTC). Q: Is DTC P0171 set? YES: Replace the ECM or PCM. Then go to Step 14. NO: The procedure is complete.
STEP 14. Perform the OBD-II drive cycle.
Carry out a test drive with the drive cycle pattern. Refer to Trouble Code Diagnosis- OBD-II Drive Cycle - Procedure 2 - Fuel Trim Monitor.
Check the diagnostic trouble code (DTC). Q: Is DTC P0171 set? YES: Repeat the troubleshooting. NO: The procedure is complete.
Sep 23, 2007, 02:28 AM
#5
did you read the other thread i made about rough idle??? I had the exact same code. If you have ever removed the injectors from the intake manifold you should replace the rubber spacers that make the seal between injector and the mani. Bring it down to your auto store and they should have replacements for it. Make sure its FUEL RATED or else it will deteriorate quickly.
Sep 23, 2007, 08:07 AM
#7
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remove the FPR and throw a bottle of fuel injector cleaner in the tank. drive around for a bit and see if the code comes back.
i was getting one of the injector circuit malfunction codes the other day and i had to pull the fuel rail and injectors and give them a good cleaning. that appeared to do it for me though.
i was getting one of the injector circuit malfunction codes the other day and i had to pull the fuel rail and injectors and give them a good cleaning. that appeared to do it for me though.
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Sep 23, 2007, 10:33 AM
#9
well i haven't touched my injectors, and i have no idea what the fuel pressure is at cos i don't got a gauge.
i will run some seafoam through the fuel system and see if that helps. I am planning on replacing the FPR, injectors and fuel rail when i go turbo (hopefully not to much longer) so i may just leave it be, my car seems to be running fine.
also i can't remove the FPR cos the bolt head snapped off when i installed it. Which is why i'm replacing the entire fuel rail
how do i adjust the pressure on those generic FPRs?
pics of fpr:
i will run some seafoam through the fuel system and see if that helps. I am planning on replacing the FPR, injectors and fuel rail when i go turbo (hopefully not to much longer) so i may just leave it be, my car seems to be running fine.
also i can't remove the FPR cos the bolt head snapped off when i installed it. Which is why i'm replacing the entire fuel rail
how do i adjust the pressure on those generic FPRs?
pics of fpr:
Last edited by crypto; Sep 23, 2007 at 10:49 AM.
Sep 23, 2007, 11:03 AM
#10
well i haven't touched my injectors, and i have no idea what the fuel pressure is at cos i don't got a gauge.
i will run some seafoam through the fuel system and see if that helps. I am planning on replacing the FPR, injectors and fuel rail when i go turbo (hopefully not to much longer) so i may just leave it be, my car seems to be running fine.
also i can't remove the FPR cos the bolt head snapped off when i installed it. Which is why i'm replacing the entire fuel rail
how do i adjust the pressure on those generic FPRs?
pics of fpr:
i will run some seafoam through the fuel system and see if that helps. I am planning on replacing the FPR, injectors and fuel rail when i go turbo (hopefully not to much longer) so i may just leave it be, my car seems to be running fine.
also i can't remove the FPR cos the bolt head snapped off when i installed it. Which is why i'm replacing the entire fuel rail
how do i adjust the pressure on those generic FPRs?
pics of fpr:
Sep 23, 2007, 12:08 PM
#13
well yesterday i tried clearing the code and then started the car up, and the light came back a minute later.
I just increased the fuel pressure and cleared the code. After 10 mins of idling the code isn't even pending. So i can only assume i fixed it.
We shall see how it goes when i start driving
I just increased the fuel pressure and cleared the code. After 10 mins of idling the code isn't even pending. So i can only assume i fixed it.
We shall see how it goes when i start driving
Nov 3, 2008, 09:12 AM
#15
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damn im getting this code now too. and im thinking its piggyback but yours wasnt piggyback. mods: cai, 2 1/2 high flow cat 2 1/2 piping on exhaust, header and o2 put after cat so the dumb rich code would go away pigguback v1 and rrm crank pulley. trying to figure out how to get rid of it. im also gettin p0141 as good luck runs it. which is 02 heater circuit malfunction. think its as simple as my 02 gone bad? or maybe piggyback or maf or even cai? any help would be appreciated.