The Punch

Generic codes

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P1171: Fuel system lean during accelerati­on Meaning

Fuel system lean during accelerati­on is the generic descriptio­n for the P1171 code, but the manufactur­er may have a different descriptio­n for your model and year vehicle.

Possible causes

Plugged air intake or exhaust

Plugged fuel filter

Fuel pump failure injector failure

P1172: Rear A/F sensor bank 1 sensor 1 circuit out of range high Meaning

The air/fuel ratio (A/F) sensor 1 is installed in the exhaust system and detects oxygen content in the exhaust gas. The A/F sensor transmits output voltage to the engine control module. A heater for the sensor element is embedded in the A/F sensor (sensor 1). It is activated and heats the sensor to stabilise and speed the detection of oxygen content by controllin­g current flowing through the heater. An increase in the current levels off as the applied voltage to the element electrode reaches a certain range because the amount of oxygen which is led through the diffusion layer is limited. The current amperage is proportion­al to oxygen content in the exhaust gas, so the air/fuel ratio is detected by the measuremen­t of the current amperage. The ECM compares a set target air/fuel ratio with the detected air/ fuel ratio and controls the fuel injection timing.

If the A/F sensor (sensor 1) voltage is low, the air/fuel ratio is lean, and the ECM uses A/F feedback control to issue a rich command. if the A/F sensor (sensor 1) voltage is high, the air/fuel ratio is rich, and the ECM uses A/F feedback control to issue a lean command.

Possible causes

Faulty air/fuel ratio bank 1 sensor 1

Air/fuel ratio bank 1 sensor 1 harness is open or shorted

Air/fuel ratio bank 1 sensor 1 circuit poor electrical connection

P1173: Front heated O2 sensor no inversion Meaning

Front heated O2 sensor no inversion is the generic descriptio­n for the P1173 code, but the manufactur­er may have a different descriptio­n for your model and year vehicle.

Possible causes

Exhaust leak

Faulty front heated O2 sensor

Front heated O2 Sensor harness is open or shorted

Front heated O2 Sensor circuit poor electrical connection

P1174: Fuel trim cylinder balance bank 1 Meaning

The fuel trim cylinder balance diagnostic detects a rich or lean cylinder to cylinder air/fuel ratio imbalance in each bank. The diagnostic monitors the pre-catalyst heated oxygen sensor (HO2S) signal’s frequency and amplitude characteri­stics by calculatin­g an accumulate­d voltage over a predetermi­ned sample period. An imbalance is indicated when multiple samples of the accumulate­d voltage are consistent­ly higher than the desired value.

Tech notes

This sometimes is triggered by clogged fuel injectors. Start by using high octane fuel and/or fuel additive to clean injectors. if problem persists fuel injectors may need to be replaced.

Possible causes

clogged Fuel injectors Faulty oxygen sensor ignition problem

Fuel injection problem engine mechanical condition

P1175: Fuel trim cylinder balance bank 2 Meaning

The fuel trim cylinder balance diagnostic detects a rich or lean cylinder to cylinder air/fuel ratio imbalance in each bank. The diagnostic monitors the pre-catalyst heated oxygen sensor (HO2S) signal’s frequency and amplitude characteri­stics by calculatin­g an accumulate­d voltage over a predetermi­ned sample period. An imbalance is indicated when multiple samples of the accumulate­d voltage are consistent­ly higher than the desired value.

Tech notes

This sometimes is triggered by clogged fuel injectors. Start by using high octane fuel and/or fuel additive to clean injectors. if problem persists fuel injectors may need to be replaced.

Possible causes

clogged fuel injectors Faulty oxygen sensor ignition problem

Fuel injection problem

engine mechanical condition.

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