Acura RL. Manual - part 6

Fig. 18: Cooling System - Operation Diagram 

General Description 

The thermostat is closed when the engine coolant temperature is low, and it stops the circulation of engine 
coolant to speed engine warm up. When the engine coolant temperature increases, the thermostat opens and 
circulates engine coolant to control its temperature. When the engine coolant temperature decreases, the 
opening area of the thermostat is reduced to regulate the engine coolant temperature. If the thermostat sticks 
open, engine warm up is delayed, and exhaust emissions are adversely affected. The powertrain control 
module (PCM) measures the rise in the coolant temperature after the engine starts using engine coolant 
temperature (ECT) sensors 1/2, and it estimates the characteristics of the engine coolant temperature by 
calculations based on those two temperatures and the driving conditions. When ECT 2 immediately 
increases from the starting value, it is defined as the thermostat stuck open. When ECT 2 does not increase 
to the specified value, it is defined as a thermostat malfunction. 

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

MONITOR DESCRIPTION CHART 

Execution

Once per driving cycle

Sequence

None

Duration

Depending on driving conditions

DTC Type

Two drive cycles, MIL ON

 

2007 Acura RL 

2007 ENGINE PERFORMANCE Advanced Diagnostics - RL

  

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Enable Conditions 

ENABLE CONDITIONS 

Malfunction Threshold 

Malfunction determination 1: 

If the difference between the current measured coolant temperature at the radiator (ECT 2) and the initial 
coolant temperature at the radiator (ECT 2) is at least 51°F (11°C) when the estimated coolant temperature 
at the engine (ECT 1) reaches 164°F (74°C), a malfunction is detected (thermostat stuck open); or if the 
coolant temperature at the radiator (ECT 2) only reaches 68°F (20°C), a malfunction is detected (thermostat 
malfunction). 

Malfunction determination 2: 

When the estimated engine coolant temperature (ECT 1) reaches 158°F (70°C) before the measured engine 
coolant temperature (ECT 1) reaches 158°F (70°C), a malfunction is detected. 

Driving Pattern 

OBD Status

PASSED/FAILED/NOT COMPLETED (STILL TESTING)

Condition

Minimum

Maximum

Elapsed time before starting the 
engine

6 hours

-

Initial engine coolant temperature 
(ECT 1)

20°F (-6°C)

123°F (50°C)

Initial engine coolant temperature 
(ECT 2)

20°F (-6°C)

-

Initial intake air temperature

20°F (-6°C)

-

The difference between initial 
intake air temperature and current 
intake air temperature

-

1°F (1°C)

(1)

3°F (2°C)

(2)

No active DTCs

P0107, P0108, P0111, P0112, P0113, P0116, P0117, P0118, 
P0122, P0123, P0125, P0134, P0135, P0154, P0155, P0171, 
P0172, P0174, P0175, P0222, P0223, P0300, P0301, P0302, 
P0303, P0304, P0305, P0306, P0335, P0339, P0340, P0344, 
P0401, P0404, P0443, P0496, P0506, P0507, P0627, P1077, 
P1078, P1109, P1116, P1128, P1129, P1172, P1174, P2101, 
P2108, P2118, P2122, P2123, P2127, P2128, P2135, P2138, 
P2176, P2183, P2184, P2185, P2195, P2197, P2227, P2228, 
P2229, P2237, P2238, P2240, P2241, P2243, P2245, P2247, 
P2249, P2251, P2252, P2254, P2255, P2413, P2610, P2627, 
P2628, P2630, P2631, P2646, P2647, P2648, P2649, U0107

(1)

Intake air temperature decrease judgement when there is no driving record 25 mph (40 km/h) in 
this drive cycle.

(2)

Intake air temperature decrease judgement when there is a driving record 25 mph (40 km/h) in 
this drive cycle.

 

2007 Acura RL 

2007 ENGINE PERFORMANCE Advanced Diagnostics - RL

  

me 

 

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1. Start the engine under the conditions specified under Enable Conditions.  

2. Drive the vehicle at a speed between 15 - 75 mph (24 - 120 km/h) for at least 10 minutes.  



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 with the ECT and IAT at engine start-up within 
the specified temperature range, a Temporary DTC is stored in the PCM memory. If the malfunction recurs 
during the next (second) drive cycle with the ECT and IAT at engine start-up within the specified 
temperature range, 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 trips in which the 
diagnostic runs. 

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 P0133 (157): ADVANCED DIAGNOSTICS 

DTC P0133: REAR AIR/FUEL RATIO (A/F) SENSOR (BANK 1, SENSOR 1) CIRCUIT SLOW 
RESPONSE 

 

2007 Acura RL 

2007 ENGINE PERFORMANCE Advanced Diagnostics - RL

  

me 

 

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Fig. 19: Rear Air/Fuel Ratio Sensor (Bank 1, Sensor 1) Signal Output

General Description 

The rear air/fuel ratio (A/F) sensor (bank 1, sensor 1) has a linear signal output in relation to the oxygen 
concentration. The powertrain control module (PCM) computes the air/fuel ratio from rear A/F sensor 
output voltage and uses fuel feedback control to improve exhaust emissions. The PCM measures the 
response characteristics against the rear A/F sensor output, and if the average inversion cycle time is less 
than the specified value, it detects a deteriorated response and stores a DTC. 

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

MONITOR DESCRIPTION CHART 

Enable Conditions 

ENABLE CONDITIONS 

Malfunction Threshold 

The average of the rear A/F sensor (bank 1, sensor 1) inversion cycle 11 periods or less is at least 6.8 

Execution

Once per driving cycle

Sequence

None

Duration

6.8 seconds or more

DTC Type

Two drive cycles, MIL ON

OBD Status

PASSED/FAILED/EXECUTING/OUT OF (TEST) CONDITION

Condition

Minimum

Maximum

Engine coolant temperature

156°F (69°C)

-

Intake air temperature

15°F (-9°C)

-

Engine speed

1,250 rpm

2,200 rpm

MAP value

1,250 rpm

47 kPa (13.8 in.Hg, 350 
mmHg)

69 kPa (20.4 in.Hg, 520 
mmHg)

2,000 rpm

27 kPa (7.9 in.Hg, 200 
mmHg)

Vehicle speed

33 mph (52 km/h)

-

Fuel trim

0.73

1.47

Fuel feedback

Closed loop at stoichiometric

Monitoring priority

P0456, P0457, P0497

No active DTCs

P0107, P0108, P0112, P0113, P0117, P0118, 
P0134, P0135, P0171, P0172, P0300, P0301, 
P0302, P0303, P0304, P0305, P0306, P0335, 
P0339, P0340, P0344, P0401, P0404, P0443, 
P0496, P0627, P1077, P1078, P1109, P1128, 
P1129, P1172, P2195, P2227, P2228, P2229, 
P2237, P2238, P2243, P2245, P2251, P2252, 
P2413, P2627, P2628, P2646, P2647, P2648, 
P2649, P2A00

Other

Without excessive load change

 

2007 Acura RL 

2007 ENGINE PERFORMANCE Advanced Diagnostics - RL

  

me 

 

Friday, June 05, 2009 2:32:03 PM

Page 24 

© 2005 Mitchell Repair Information Company, LLC.