Acura RL. Manual - part 14

Fig. 40: Front Secondary Heated Oxygen Sensor (Secondary HO2S) (Bank 2, Sensor 2) Heater -
Circuit Diagram

General Description

A heater for the zirconia element is embedded in the front secondary heated oxygen sensor (front secondary
HO2S) (bank 2, sensor 2) and is controlled by the powertrain control module (PCM). When activated, it
heats the sensor to stabilize and speed up the detection of oxygen content when the exhaust gas temperature
is cold.

If the front secondary HO2S heater draws more or less than a specified amperage, the PCM detects a
malfunction and stores a DTC.

Monitor Execution, Sequence, Duration, DTC Type, OBD Status

MONITOR DESCRIPTION CHART

Enable Conditions

ENABLE CONDITIONS

Execution

Continuous

Sequence

None

Duration

5 seconds or more

DTC Type

One drive cycle, MIL ON

OBD Status

PASSED/FAILED/NOT COMPLETED (STILL TESTING)

Condition

Minimum

Maximum

Battery voltage
(IGP terminal of PCM)

10.5 V

16 V

State of the engine

Running

No active DTCs

P0117, P0118

2007 Acura RL

2007 ENGINE PERFORMANCE Advanced Diagnostics - RL

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Malfunction Threshold

The front secondary HO2S heater output is 0.38 A or less, or 3.33 A or more, for at least 5 seconds when the
heater is on.

Driving Pattern

Start the engine. Hold the engine speed at 3,000 rpm without load (in Park or neutral) until the radiator fan
comes on, then let it idle.

Diagnosis Details

Conditions for illuminating the MIL

When a malfunction is detected, the MIL comes on and the DTC and the freeze frame data are stored in the
PCM memory.

Conditions for clearing the MIL

The MIL will be cleared if the malfunction does not recur during three consecutive trips in which the
diagnostic runs.

The MIL, the DTC, and the freeze frame data can be cleared by using the scan tool Clear command or by
disconnecting the battery.

DTC P0171 (153): ADVANCED DIAGNOSTICS

DTC P0171: REAR BANK (BANK 1) FUEL SYSTEM TOO LEAN

Fig. 41: Rear Bank (Bank 1) Fuel System Too Lean Air Fuel Ratio

General Description

Long term fuel trim is computed from short term fuel trim and is used to regulate long term deviation from
the stoichiometric air/fuel ratio, which occurs when fuel metering components deteriorate with age or
system failures occur. In addition, long term fuel trim is stored in the PCM memory and is used to determine

2007 Acura RL

2007 ENGINE PERFORMANCE Advanced Diagnostics - RL

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when fuel metering components malfunction. When long term fuel trim is higher than normal, which is
about 1.0 (0%), the amount of injected fuel must be increased, and when lower than normal, it must be
decreased. If long term fuel trim is higher than normal (too lean), a malfunction in the fuel metering
components is detected and a DTC is stored.

Monitor Execution, Sequence, Duration, DTC Type, OBD Status

MONITOR DESCRIPTION CHART

Enable Conditions

ENABLE CONDITIONS

Malfunction Threshold

Long term fuel trim is higher than 1.19 (+19%).

Driving Pattern

1. Start the engine. Hold the engine speed at 3,000 rpm without load (in Park or neutral) until the

radiator fan comes on.

2. Then, drive at a steady speed between 15 - 75 mph (24 - 120 km/h) for at least 15 minutes, and watch

the long term fuel trim. If the long term fuel trim stays at about 1.0, the vehicle is OK or it is a very
minor problem. If a significant fault is still present, the long term fuel trim will move up or down
while driving.



When freeze frame data is stored, drive the vehicle under those conditions instead of Driving Pattern
2.

Execution

Once per driving cycle

(1)

Sequence

None

Duration

Every 7 seconds

DTC Type

Two drive cycles, MIL ON

OBD Status

N/A

(1)

The malfunction judgment is cleared when it is judged as normal under the same driving
conditions in which the malfunction was detected.

Condition

Minimum

Maximum

Engine coolant temperature

156°F (69°C)

Intake air temperature

32°F (0°C)

Engine speed

580 rpm

4,000 rpm

MAP value

22 kPa (6.3 in.Hg, 160 mmHg)

Fuel feedback

Closed loop

Monitoring priority

P0420, P0430, P0456, P0457

No active DTCs

P0107, P0108, P0112, P0113, P0117, P0118, P0134, P0135,
P0137, P0138, P0300, P0301, P0302, P0303, P0304, P0305,
P0306, P0335, P0339, P0401, P0404, P0443, P0496, P0627,
P1077, P1078, P1109, P1128, P1129, P1172, P2195, P2227,
P2228, P2229, P2237, P2238, P2243, P2245, P2251, P2252,
P2270, P2271, P2413, P2627, P2628, P2646, P2647, P2648, P2649

2007 Acura RL

2007 ENGINE PERFORMANCE Advanced Diagnostics - RL

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

If the EVAP monitor runs instead of the HO2S monitor, turn the engine off, then restart it, and the
HO2S monitor will restart.



After clearing the DTC by disconnecting the battery or using the scan tool, extend Driving Pattern 2 to
40 minutes or longer to allow time for long term fuel trim to recover.



Drive the vehicle in this manner only if the traffic regulations and ambient conditions allow.

Diagnosis Details

Conditions for illuminating the MIL

When a malfunction is detected during the first drive cycle, a Temporary DTC is stored in the PCM
memory. If the malfunction recurs during the next (second) drive cycle, the MIL comes on and the DTC and
the freeze frame data are stored.

Conditions for clearing the MIL

The MIL will be cleared if the malfunction does not recur during three consecutive drive cycles in which the
engine conditions are similar to the first time the malfunction was detected.

The MIL, the DTC, the Temporary DTC, and the freeze frame data can be cleared by using the scan tool
Clear command or by disconnecting the battery.

DTC P0172 (153): ADVANCED DIAGNOSTICS

DTC P0172: REAR BANK (BANK 1) FUEL SYSTEM TOO RICH

Fig. 42: Rear Bank (Bank 1) Fuel System Too Rich Air Fuel Ratio

General Description

The powertrain control module (PCM) detects the oxygen content in the exhaust gas from the rear air/fuel
ratio (A/F) sensor (bank 1, sensor 1) signal voltage, and it performs fuel feedback control to maintain the
optimal air/fuel ratio. The air/fuel ratio coefficient for correcting the amount of injected fuel is the short term
fuel trim. The PCM varies short term fuel trim continuously to keep the air/fuel ratio close to the
stoichiometric ratio for all driving conditions. Long term fuel trim is computed from short term fuel trim and
is used to regulate long term deviation from the stoichiometric air/fuel ratio, which occurs when fuel
metering components deteriorate with age or system failures occur. In addition, long term fuel trim is stored
in the PCM memory and is used to determine when fuel metering components malfunction. When long term
fuel trim is higher than normal, which is about 1.0 (0%), the amount of injected fuel must be increased, and
when lower than normal, it must be decreased. If long term fuel trim is lower than normal (too rich), a
malfunction in the fuel metering components is detected and a DTC is stored.

2007 Acura RL

2007 ENGINE PERFORMANCE Advanced Diagnostics - RL

Friday, June 05, 2009 2:32:03 PM

Page 56

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