Code
P0172
Generic
P — Powertrain
System Too Rich Bank 1
Views:
UK: 33
EN: 44
RU: 42
AI status
Completed
Completed
100%
Causes
- Leaking or stuck-open fuel injector(s) on bank 1
- High fuel pressure (faulty fuel pressure regulator or return restriction)
- Contaminated or faulty mass airflow (MAF) sensor
- Faulty intake air temperature (IAT) or engine coolant temperature (ECT) sensor reporting cold
- Faulty upstream oxygen sensor (HO2S) or sensor wiring shorted to voltage
- Incorrect fuel trim due to ECU or software faults (rare)
Symptoms
- Check Engine Light illuminated
- Poor fuel economy
- Black smoke from exhaust or strong fuel smell
- Rough idle or hesitation on acceleration
- Fouled or blackened spark plugs on bank 1
- Possible drivability problems (misfire, stumble)
What to check
- Read stored freeze-frame and live data (LTFT/STFT for bank 1, O2 voltages, MAF grams/sec or volts, fuel trims)
- Inspect for obvious fuel leaks and sniff for fuel smell around injectors and rail
- Visually inspect air intake, air filter, and MAF sensor for contamination or damage
- Measure fuel rail pressure with a gauge at key-on/run and during idle and load
- Check upstream O2 sensor behavior (voltage should switch; a constant high voltage ~0.8–1.0 V may indicate rich or a bad sensor)
- Inspect wiring and connectors for injectors, MAF, O2, ECT/IAT and fuel pressure regulator
Signal parameters
- Long Term Fuel Trim (LTFT) Bank 1: significantly negative (example:
- Short Term Fuel Trim (STFT) Bank 1: sustained negative values (example: -10% or lower under steady conditions)
- Upstream O2 (HO2S) Bank 1 voltage: steady high (~0.7–1.0 V) or non-switching when it should oscillate
- MAF sensor: unexpected low airflow reading for given RPM/load (g/s or V out of expected range) or intermittent signal
- Fuel rail pressure: above factory spec (varies by system; consult vehicle spec — e.g., > nominal by ~10% can cause richness)
- Engine coolant temp or IAT: sensor reporting higher than actual cold reading (ECU sees colder than actual => enrichment)
Diagnostic algorithm
- Retrieve freeze-frame data and live PID values: note LTFT/STFT bank 1, MAF, fuel pressure, O2 voltages, ECT/IAT.
- Visually inspect intake and MAF; clean MAF with recommended cleaner if contaminated, then retest.
- Check for vacuum leaks (while leaks usually cause lean codes, verify none are causing incorrect sensor readings).
- Test fuel pressure at the rail at idle and during snap throttle; compare to spec. If high, inspect fuel pressure regulator and return line.
- Perform an injector leak test or fuel injector balance test on bank 1; look for leaking or over-delivering injector(s).
- Monitor upstream O2 sensor: command a rich/lean response (if vehicle supports) or watch voltage with throttle changes. Replace if sensor is stuck high and other causes ruled out.
- Inspect and test IAT and ECT sensors for correct resistance/voltage vs temperature. Replace if reading incorrectly cold.
- Disconnect MAF (or substitute with known-good) and observe fuel trims: if trims normalize when MAF disconnected, suspect MAF sensor or intake metering issue.
- Check injector wiring and driver outputs with a scope or meter for proper pulse and no leakage to ground.
- Clear codes and test drive to verify repair. If code returns, follow targeted tests based on final suspicious component(s).
Likely causes
- Stuck-open or leaking injector(s) on bank 1 (most common)
- Excessive fuel rail pressure from a bad regulator or clogged return
- MAF under-reporting airflow because of contamination or failure
- Faulty coolant or intake air temp sensor commanding enrichment
- Upstream O2 sensor stuck high (falsely indicating rich)
- Fuel system return line restriction or collapsed hose
Fault status
Status
ECM detects bank 1 running richer than calibrated threshold (excess fuel / insufficient air) — corrective action required to prevent catalyst damage and poor fuel economy.
Repair difficulty: Medium
Diagnostic time: 1.0-3.0 hours
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Code
P0172
GWM
P — Powertrain
- A mixture of rich (bank 1)
Views:
UK: 23
EN: 30
RU: 27
AI status
Completed
Completed
100%
Causes
- Leaking or stuck-open fuel injector(s) on bank 1
- High fuel pressure (faulty fuel pressure regulator or return restriction)
- Contaminated or faulty mass airflow (MAF) sensor
- Faulty intake air temperature (IAT) or engine coolant temperature (ECT) sensor reporting cold
- Faulty upstream oxygen sensor (HO2S) or sensor wiring shorted to voltage
- Incorrect fuel trim due to ECU or software faults (rare)
Symptoms
- Check Engine Light illuminated
- Poor fuel economy
- Black smoke from exhaust or strong fuel smell
- Rough idle or hesitation on acceleration
- Fouled or blackened spark plugs on bank 1
- Possible drivability problems (misfire, stumble)
What to check
- Read stored freeze-frame and live data (LTFT/STFT for bank 1, O2 voltages, MAF grams/sec or volts, fuel trims)
- Inspect for obvious fuel leaks and sniff for fuel smell around injectors and rail
- Visually inspect air intake, air filter, and MAF sensor for contamination or damage
- Measure fuel rail pressure with a gauge at key-on/run and during idle and load
- Check upstream O2 sensor behavior (voltage should switch; a constant high voltage ~0.8–1.0 V may indicate rich or a bad sensor)
- Inspect wiring and connectors for injectors, MAF, O2, ECT/IAT and fuel pressure regulator
Signal parameters
- Long Term Fuel Trim (LTFT) Bank 1: significantly negative (example:
- Short Term Fuel Trim (STFT) Bank 1: sustained negative values (example: -10% or lower under steady conditions)
- Upstream O2 (HO2S) Bank 1 voltage: steady high (~0.7–1.0 V) or non-switching when it should oscillate
- MAF sensor: unexpected low airflow reading for given RPM/load (g/s or V out of expected range) or intermittent signal
- Fuel rail pressure: above factory spec (varies by system; consult vehicle spec — e.g., > nominal by ~10% can cause richness)
- Engine coolant temp or IAT: sensor reporting higher than actual cold reading (ECU sees colder than actual => enrichment)
Diagnostic algorithm
- Retrieve freeze-frame data and live PID values: note LTFT/STFT bank 1, MAF, fuel pressure, O2 voltages, ECT/IAT.
- Visually inspect intake and MAF; clean MAF with recommended cleaner if contaminated, then retest.
- Check for vacuum leaks (while leaks usually cause lean codes, verify none are causing incorrect sensor readings).
- Test fuel pressure at the rail at idle and during snap throttle; compare to spec. If high, inspect fuel pressure regulator and return line.
- Perform an injector leak test or fuel injector balance test on bank 1; look for leaking or over-delivering injector(s).
- Monitor upstream O2 sensor: command a rich/lean response (if vehicle supports) or watch voltage with throttle changes. Replace if sensor is stuck high and other causes ruled out.
- Inspect and test IAT and ECT sensors for correct resistance/voltage vs temperature. Replace if reading incorrectly cold.
- Disconnect MAF (or substitute with known-good) and observe fuel trims: if trims normalize when MAF disconnected, suspect MAF sensor or intake metering issue.
- Check injector wiring and driver outputs with a scope or meter for proper pulse and no leakage to ground.
- Clear codes and test drive to verify repair. If code returns, follow targeted tests based on final suspicious component(s).
Likely causes
- Stuck-open or leaking injector(s) on bank 1 (most common)
- Excessive fuel rail pressure from a bad regulator or clogged return
- MAF under-reporting airflow because of contamination or failure
- Faulty coolant or intake air temp sensor commanding enrichment
- Upstream O2 sensor stuck high (falsely indicating rich)
- Fuel system return line restriction or collapsed hose
Fault status
Status
ECM detects bank 1 running richer than calibrated threshold (excess fuel / insufficient air) — corrective action required to prevent catalyst damage and poor fuel economy.
Repair difficulty: Medium
Diagnostic time: 1.0-3.0 hours
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Code
P0172
HUMMER
P — Powertrain
Fuel Trim System Rich Bank 1
Views:
UK: 18
EN: 35
RU: 31
AI status
Completed
Completed
100%
Causes
- Leaking or stuck-open fuel injector(s) on bank 1
- High fuel pressure (faulty fuel pressure regulator or return restriction)
- Contaminated or faulty mass airflow (MAF) sensor
- Faulty intake air temperature (IAT) or engine coolant temperature (ECT) sensor reporting cold
- Faulty upstream oxygen sensor (HO2S) or sensor wiring shorted to voltage
- Incorrect fuel trim due to ECU or software faults (rare)
Symptoms
- Check Engine Light illuminated
- Poor fuel economy
- Black smoke from exhaust or strong fuel smell
- Rough idle or hesitation on acceleration
- Fouled or blackened spark plugs on bank 1
- Possible drivability problems (misfire, stumble)
What to check
- Read stored freeze-frame and live data (LTFT/STFT for bank 1, O2 voltages, MAF grams/sec or volts, fuel trims)
- Inspect for obvious fuel leaks and sniff for fuel smell around injectors and rail
- Visually inspect air intake, air filter, and MAF sensor for contamination or damage
- Measure fuel rail pressure with a gauge at key-on/run and during idle and load
- Check upstream O2 sensor behavior (voltage should switch; a constant high voltage ~0.8–1.0 V may indicate rich or a bad sensor)
- Inspect wiring and connectors for injectors, MAF, O2, ECT/IAT and fuel pressure regulator
Signal parameters
- Long Term Fuel Trim (LTFT) Bank 1: significantly negative (example:
- Short Term Fuel Trim (STFT) Bank 1: sustained negative values (example: -10% or lower under steady conditions)
- Upstream O2 (HO2S) Bank 1 voltage: steady high (~0.7–1.0 V) or non-switching when it should oscillate
- MAF sensor: unexpected low airflow reading for given RPM/load (g/s or V out of expected range) or intermittent signal
- Fuel rail pressure: above factory spec (varies by system; consult vehicle spec — e.g., > nominal by ~10% can cause richness)
- Engine coolant temp or IAT: sensor reporting higher than actual cold reading (ECU sees colder than actual => enrichment)
Diagnostic algorithm
- Retrieve freeze-frame data and live PID values: note LTFT/STFT bank 1, MAF, fuel pressure, O2 voltages, ECT/IAT.
- Visually inspect intake and MAF; clean MAF with recommended cleaner if contaminated, then retest.
- Check for vacuum leaks (while leaks usually cause lean codes, verify none are causing incorrect sensor readings).
- Test fuel pressure at the rail at idle and during snap throttle; compare to spec. If high, inspect fuel pressure regulator and return line.
- Perform an injector leak test or fuel injector balance test on bank 1; look for leaking or over-delivering injector(s).
- Monitor upstream O2 sensor: command a rich/lean response (if vehicle supports) or watch voltage with throttle changes. Replace if sensor is stuck high and other causes ruled out.
- Inspect and test IAT and ECT sensors for correct resistance/voltage vs temperature. Replace if reading incorrectly cold.
- Disconnect MAF (or substitute with known-good) and observe fuel trims: if trims normalize when MAF disconnected, suspect MAF sensor or intake metering issue.
- Check injector wiring and driver outputs with a scope or meter for proper pulse and no leakage to ground.
- Clear codes and test drive to verify repair. If code returns, follow targeted tests based on final suspicious component(s).
Likely causes
- Stuck-open or leaking injector(s) on bank 1 (most common)
- Excessive fuel rail pressure from a bad regulator or clogged return
- MAF under-reporting airflow because of contamination or failure
- Faulty coolant or intake air temp sensor commanding enrichment
- Upstream O2 sensor stuck high (falsely indicating rich)
- Fuel system return line restriction or collapsed hose
Fault status
Status
ECM detects bank 1 running richer than calibrated threshold (excess fuel / insufficient air) — corrective action required to prevent catalyst damage and poor fuel economy.
Repair difficulty: Medium
Diagnostic time: 1.0-3.0 hours
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Code
P0172
LAND ROVER
P — Powertrain
System too rich (bank 1)
Views:
UK: 15
EN: 30
RU: 29
AI status
Completed
Completed
100%
Causes
- Leaking or stuck-open fuel injector(s) on bank 1
- High fuel pressure (faulty fuel pressure regulator or return restriction)
- Contaminated or faulty mass airflow (MAF) sensor
- Faulty intake air temperature (IAT) or engine coolant temperature (ECT) sensor reporting cold
- Faulty upstream oxygen sensor (HO2S) or sensor wiring shorted to voltage
- Incorrect fuel trim due to ECU or software faults (rare)
Symptoms
- Check Engine Light illuminated
- Poor fuel economy
- Black smoke from exhaust or strong fuel smell
- Rough idle or hesitation on acceleration
- Fouled or blackened spark plugs on bank 1
- Possible drivability problems (misfire, stumble)
What to check
- Read stored freeze-frame and live data (LTFT/STFT for bank 1, O2 voltages, MAF grams/sec or volts, fuel trims)
- Inspect for obvious fuel leaks and sniff for fuel smell around injectors and rail
- Visually inspect air intake, air filter, and MAF sensor for contamination or damage
- Measure fuel rail pressure with a gauge at key-on/run and during idle and load
- Check upstream O2 sensor behavior (voltage should switch; a constant high voltage ~0.8–1.0 V may indicate rich or a bad sensor)
- Inspect wiring and connectors for injectors, MAF, O2, ECT/IAT and fuel pressure regulator
Signal parameters
- Long Term Fuel Trim (LTFT) Bank 1: significantly negative (example:
- Short Term Fuel Trim (STFT) Bank 1: sustained negative values (example: -10% or lower under steady conditions)
- Upstream O2 (HO2S) Bank 1 voltage: steady high (~0.7–1.0 V) or non-switching when it should oscillate
- MAF sensor: unexpected low airflow reading for given RPM/load (g/s or V out of expected range) or intermittent signal
- Fuel rail pressure: above factory spec (varies by system; consult vehicle spec — e.g., > nominal by ~10% can cause richness)
- Engine coolant temp or IAT: sensor reporting higher than actual cold reading (ECU sees colder than actual => enrichment)
Diagnostic algorithm
- Retrieve freeze-frame data and live PID values: note LTFT/STFT bank 1, MAF, fuel pressure, O2 voltages, ECT/IAT.
- Visually inspect intake and MAF; clean MAF with recommended cleaner if contaminated, then retest.
- Check for vacuum leaks (while leaks usually cause lean codes, verify none are causing incorrect sensor readings).
- Test fuel pressure at the rail at idle and during snap throttle; compare to spec. If high, inspect fuel pressure regulator and return line.
- Perform an injector leak test or fuel injector balance test on bank 1; look for leaking or over-delivering injector(s).
- Monitor upstream O2 sensor: command a rich/lean response (if vehicle supports) or watch voltage with throttle changes. Replace if sensor is stuck high and other causes ruled out.
- Inspect and test IAT and ECT sensors for correct resistance/voltage vs temperature. Replace if reading incorrectly cold.
- Disconnect MAF (or substitute with known-good) and observe fuel trims: if trims normalize when MAF disconnected, suspect MAF sensor or intake metering issue.
- Check injector wiring and driver outputs with a scope or meter for proper pulse and no leakage to ground.
- Clear codes and test drive to verify repair. If code returns, follow targeted tests based on final suspicious component(s).
Likely causes
- Stuck-open or leaking injector(s) on bank 1 (most common)
- Excessive fuel rail pressure from a bad regulator or clogged return
- MAF under-reporting airflow because of contamination or failure
- Faulty coolant or intake air temp sensor commanding enrichment
- Upstream O2 sensor stuck high (falsely indicating rich)
- Fuel system return line restriction or collapsed hose
Fault status
Status
ECM detects bank 1 running richer than calibrated threshold (excess fuel / insufficient air) — corrective action required to prevent catalyst damage and poor fuel economy.
Repair difficulty: Medium
Diagnostic time: 1.0-3.0 hours
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Code
P0172
MITSUBISHI
P — Powertrain
Fuel trim -Åtoo rich
Views:
UK: 16
EN: 31
RU: 33
AI status
Completed
Completed
100%
Causes
- Leaking or stuck-open fuel injector(s) on bank 1
- High fuel pressure (faulty fuel pressure regulator or return restriction)
- Contaminated or faulty mass airflow (MAF) sensor
- Faulty intake air temperature (IAT) or engine coolant temperature (ECT) sensor reporting cold
- Faulty upstream oxygen sensor (HO2S) or sensor wiring shorted to voltage
- Incorrect fuel trim due to ECU or software faults (rare)
Symptoms
- Check Engine Light illuminated
- Poor fuel economy
- Black smoke from exhaust or strong fuel smell
- Rough idle or hesitation on acceleration
- Fouled or blackened spark plugs on bank 1
- Possible drivability problems (misfire, stumble)
What to check
- Read stored freeze-frame and live data (LTFT/STFT for bank 1, O2 voltages, MAF grams/sec or volts, fuel trims)
- Inspect for obvious fuel leaks and sniff for fuel smell around injectors and rail
- Visually inspect air intake, air filter, and MAF sensor for contamination or damage
- Measure fuel rail pressure with a gauge at key-on/run and during idle and load
- Check upstream O2 sensor behavior (voltage should switch; a constant high voltage ~0.8–1.0 V may indicate rich or a bad sensor)
- Inspect wiring and connectors for injectors, MAF, O2, ECT/IAT and fuel pressure regulator
Signal parameters
- Long Term Fuel Trim (LTFT) Bank 1: significantly negative (example:
- Short Term Fuel Trim (STFT) Bank 1: sustained negative values (example: -10% or lower under steady conditions)
- Upstream O2 (HO2S) Bank 1 voltage: steady high (~0.7–1.0 V) or non-switching when it should oscillate
- MAF sensor: unexpected low airflow reading for given RPM/load (g/s or V out of expected range) or intermittent signal
- Fuel rail pressure: above factory spec (varies by system; consult vehicle spec — e.g., > nominal by ~10% can cause richness)
- Engine coolant temp or IAT: sensor reporting higher than actual cold reading (ECU sees colder than actual => enrichment)
Diagnostic algorithm
- Retrieve freeze-frame data and live PID values: note LTFT/STFT bank 1, MAF, fuel pressure, O2 voltages, ECT/IAT.
- Visually inspect intake and MAF; clean MAF with recommended cleaner if contaminated, then retest.
- Check for vacuum leaks (while leaks usually cause lean codes, verify none are causing incorrect sensor readings).
- Test fuel pressure at the rail at idle and during snap throttle; compare to spec. If high, inspect fuel pressure regulator and return line.
- Perform an injector leak test or fuel injector balance test on bank 1; look for leaking or over-delivering injector(s).
- Monitor upstream O2 sensor: command a rich/lean response (if vehicle supports) or watch voltage with throttle changes. Replace if sensor is stuck high and other causes ruled out.
- Inspect and test IAT and ECT sensors for correct resistance/voltage vs temperature. Replace if reading incorrectly cold.
- Disconnect MAF (or substitute with known-good) and observe fuel trims: if trims normalize when MAF disconnected, suspect MAF sensor or intake metering issue.
- Check injector wiring and driver outputs with a scope or meter for proper pulse and no leakage to ground.
- Clear codes and test drive to verify repair. If code returns, follow targeted tests based on final suspicious component(s).
Likely causes
- Stuck-open or leaking injector(s) on bank 1 (most common)
- Excessive fuel rail pressure from a bad regulator or clogged return
- MAF under-reporting airflow because of contamination or failure
- Faulty coolant or intake air temp sensor commanding enrichment
- Upstream O2 sensor stuck high (falsely indicating rich)
- Fuel system return line restriction or collapsed hose
Fault status
Status
ECM detects bank 1 running richer than calibrated threshold (excess fuel / insufficient air) — corrective action required to prevent catalyst damage and poor fuel economy.
Repair difficulty: Medium
Diagnostic time: 1.0-3.0 hours
Similar codes
Your experience will help others
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Was this AI description helpful?
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