1995 ACURA TL Service Repair Manual

Troubleshooting
Troubleshooting Procedure s (cont'd )
Sympto m Char t
Liste d belo w ar e symptom s an d probabl e cause s fo r problem s tha t D O NO T caus e th e Malfunctio n Indicato r Lam p (MIL ) t o
com e on . I f th e MI L wa s reporte d on , g o to pag e 11-32 .
Troubleshoo t eac h probabl e caus e in th e orde r liste d (fro m lef t t o right ) unti l th e sympto m is eliminated .
Th e probabl e caus e an d troubleshootin g pag e referenc e ca n b e foun d o n nex t page .
SYMPTO M
Engin e wil l no t star t
Har d startin g
Col d fas t idl e to o lo w
Col d fas t idl e to o hig h
Idl e spee d fluctuate s
Misfir e o r roug h runnin g
Lo w powe r
Engin e stall s
PROBABL E CAUS E
4, 2 , 3 , 5 , 21 , 15 , 1
2 , 4 , 12 , 17 , 14 , 2 0
7, 8 , 9 , 6 , 1 7
7, 8 , 9 , 11 , 1 0
9, 7 , 8 , 11 , 1 0
Troubleshoo t fo r misfir e o n page s 11-82 , 11-8 5
2, 10 , 11 , 13 , 18 , 17 , 19 , 2 1
2, 4 , 12 , 7 , 21 , 9 , 5
Othe r Probabl e Causes for a n engin e tha t will no t start :
— Compressio n
— Intak e ai r leakag e
— Engin e locke d u p
— Timin g bel t
— Startin g syste m
— Overheatin g
— Batter y
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Probable Caus e Lis t (For the DTC Chart, see page 11-44)
Probabl e Caus e
1
2
3
4
5
6
7
8
9
10
1 1
12
13
1 4
15
1 6
17
1 8
19
2 0
2 1
Pag e
11-5 2, 11-53
11-12 4
11-131
Sectio n 2 3
See DTC chart
See DTC chart
See DTC chart
11-11 6
11-11 7
11-13 8
11-13 7
See DTC chart
See DTC chart
See DTC chart
11-11 2
11-11 1
11-13 6
11-14 2
See DTC chart
See DTC chart
System
Engin e Contro l Modul e (ECM )
Fue l pressur e
PGM-F I mai n rela y
Ignitio n syste m
Crankshaf t Position/To p Dea d Center/Cylinde r Positio n senso r circui t
Intak e Ai r Temperatur e (IAT ) senso r circui t
Idl e Ai r Contro l Valv e (IACV )
Fas t idl e therm o valv e
Idl e spee d adjustmen t
Throttle bod y
Throttl e cabl e
Mas s Ai r Flo w (MAF ) senso r
Throttl e Positio n (TP ) senso r
Barometri c pressur e (BARO ) senso r
A/ T gea r positio n signa l
Brak e switc h signa l
Ai r Cleane r
Intak e Ai r Bypas s (IAB ) contro l syste m an d intak e ai r pip e
Thre e Wa y Catalyti c Converte r (TWC )
Evaporativ e emissio n (EVAP ) contro l
Contaminate d fue l
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Troubleshooting

Troubleshooting Procedures (cont'd)

ECM Data

By connecting the OBD II scan tool or the Honda PGM Tester to the 16P data link connector (DLC), various data can be

retrieved from the ECM. The items listed in the table below conform to the SAE recommended practice.

The Honda PGM Tester also reads data beyond that recommended by SAE.

Understanding this data will help to find the causes of intermittent failures or engine problems.

NOTE:

• The "operating values" given below are approximate values and may be different depending on the environment and

the individual vehicle.

• Unless noted otherwise, "at idle speed" means idling with the engine completely warmed up, the transmission in posi-

tion or , and the A/C and all accessories turned off.

Data
Description
Operating Value

Freeze Data

Diagnostic

Trouble Code

(DTC)
If the ECM detects a problem, it will store it as a code

consisting of one letter and four numbers.

Depending on the problem, an SAE-defined code

(P0xxx)
or a
Honda-defined code
(P1xxx)
will
be
output

to the tester.
If no problem is detected,

there is no output.

Engine Speed

The ECM computes engine speed from the signals sent

from the Crankshaft Position sensor.

This data is used for determining the time and amount

of fuel injection.
Nearly the same as

tachometer indication

At idle speed:

700 ± 50 rpm

Vehicle Speed

The ECM converts pulse signals from the Vehicle

Speed Sensor (VSS) into speed data.
Nearly the same as

speedometer indication

Mass Air

Flow (MAF)
The MAF sensor measures the volume of the air that

flows into the engine, and sends voltage signals to the

ECM.
At idle speed:

2.2 - 4.4 g/sec

At 2,500 rpm with not

load:

7.5- 13.0 g/sec

Engine Coolant

Temperature

(ECT)
The ECT sensor converts coolant temperature into

voltage and signals the ECM. The sensor is a thermistor

whose internal resistance changes with coolant

temperature. The ECM uses the voltage signals from

the ECT sensor to determine the amount of injected

fuel.
With cold engine:

Same as ambient temper-

ature and IAT

With engine warmed up:

90 - 96°C

Heated Oxygen

Sensor (HO2S)

(Primary)

(Secondary)
The Heated Oxygen Sensor detects the oxygen content

in the exhaust gas and sends voltage signals to the

ECM. Based on these signals, the ECM controls the

air/fuel ratio. When the oxygen content is high (that is,

when the ratio is leaner than the stoichiometric ratio),

the voltage signal is lower. When the oxygen content is

low (that is, when the ratio is richer than the stoichio-

metric ratio), the voltage signal is higher.
0.0-1.25V

At idle speed:

about 0.1-0.9VProCarManuals.com

Data
Description

Operating Value
Freeze Data

HO2S

Feedback

Loop Status
Loop status is indicated as "open" or "closed".

Closed: Based on the HO2S output, the ECM deter-

mines the air/fuel ratio and controls the amount of

injected fuel.

Open: Ignoring HO2S output, the ECM refers to signals

from the TP, MAF, and ECT sensors to control the

amount of injected fuel.
At idle speed: closed

Short Term

Fuel Trim
The air/fuel ratio correction coefficient for correcting

the amount of injected fuel when H02S feedback is in

the closed loop status. When the signal from the H02S

is weak, short term fuel trim gets higher, and the ECM

increases the amount of injected fuel. The air/fuel ratio

gradually gets richer, causing a higher HO2S output.

Consequently, the short term fuel trim is lowered, and

the ECM reduces the amount of injected fuel. This

cycle keeps the air/fuel ratio close to the stoichiometric

ratio when in closed loop status.
±20%

Long Term

Fuel Trim
Long term fuel trim is computed from short term fuel

trim and indicates changes occurring in the fuel supply

system over a long period.

If long term fuel trim is higher than 1.00, the amount of

injected fuel must be increased. If it is lower than 1.00,

the amount of injected fuel must be reduced.
±20%

Intake Air

Temperature

(IAT)
The IAT sensor converts intake air temperature into

voltage and signals the ECM. When intake air tempera-

ture is low, the internal resistance of the sensor

increases, and the voltage signal is higher.
With cold engine:

Same as ambient temper-

ature and ECT

Throttle

Position
Based on the accelerator pedal position, the opening

angle of the throttle valve is indicated.
At idle speed:

approx. 10%

Ignition

Timing
Ignition timing is the ignition advance angle set by the

ECM. The ECM matches ignition timing to the driving

conditions.
At idle speed: 15° ±2°

BTDC with the SCS service

connector connected.

Calculated

Load Value

(CLV)
CLV is the engine load calculated from the MAF data.
At idle speed:

14-27%

At 2,500 rpm with no load:

13-26%ProCarManuals.com

Troubleshooting
Troubleshooting Procedure s (cont'd )
Sympto m Char t
Liste d belo w ar e symptom s an d probabl e cause s fo r problem s tha t D O NO T caus e th e Malfunctio n Indicato r Lam p (MIL ) t o
com e on . I f th e MI L wa s reporte d on , g o to pag e 11-32 .
Troubleshoo t eac h probabl e caus e in th e orde r liste d (fro m lef t t o right ) unti l th e sympto m is eliminated .
Th e probabl e caus e an d troubleshootin g pag e referenc e ca n b e foun d o n nex t page .
SYMPTO M
Engin e wil l no t star t
Har d startin g
Col d fas t idl e to o lo w
Col d fas t idl e to o hig h
Idl e spee d fluctuate s
Misfir e o r roug h runnin g
Lo w powe r
Engin e stall s
PROBABL E CAUS E
4, 2 , 3 , 5 , 21 , 15 , 1
2 , 4 , 12 , 17 , 14 , 2 0
7, 8 , 9 , 6 , 1 7
7, 8 , 9 , 11 , 1 0
9, 7 , 8 , 11 , 1 0
Troubleshoo t fo r misfir e o n page s 11-82 , 11-8 5
2, 10 , 11 , 13 , 18 , 17 , 19 , 2 1
2, 4 , 12 , 7 , 21 , 9 , 5
Othe r Probabl e Causes for a n engin e tha t will no t start :
— Compressio n
— Intak e ai r leakag e
— Engin e locke d u p
— Timin g bel t
— Startin g syste m
— Overheatin g
— Batter y
ProCarManuals.com

Probable Caus e Lis t (For the DTC Chart, see page 11-44)
Probabl e Caus e
1
2
3
4
5
6
7
8
9
10
1 1
12
13
1 4
15
1 6
17
1 8
19
2 0
2 1
Pag e
11-5 2, 11-53
11-12 4
11-131
Sectio n 2 3
See DTC chart
See DTC chart
See DTC chart
11-11 6
11-11 7
11-13 8
11-13 7
See DTC chart
See DTC chart
See DTC chart
11-11 2
11-11 1
11-13 6
11-14 2
See DTC chart
See DTC chart
System
Engin e Contro l Modul e (ECM )
Fue l pressur e
PGM-F I mai n rela y
Ignitio n syste m
Crankshaf t Position/To p Dea d Center/Cylinde r Positio n senso r circui t
Intak e Ai r Temperatur e (IAT ) senso r circui t
Idl e Ai r Contro l Valv e (IACV )
Fas t idl e therm o valv e
Idl e spee d adjustmen t
Throttle bod y
Throttl e cabl e
Mas s Ai r Flo w (MAF ) senso r
Throttl e Positio n (TP ) senso r
Barometri c pressur e (BARO ) senso r
A/ T gea r positio n signa l
Brak e switc h signa l
Ai r Cleane r
Intak e Ai r Bypas s (IAB ) contro l syste m an d intak e ai r pip e
Thre e Wa y Catalyti c Converte r (TWC )
Evaporativ e emissio n (EVAP ) contro l
Contaminate d fue l
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Troubleshooting
Diagnostic Troubl e Cod e (DTC ) Char t
*: Thes e DTC s wil l b e indicate d b y th e blinkin g o f th e Malfunctio n Indicato r Lam p (MIL ) wit h th e SC S servic e connecto r
connected .
*1:'95-96 model s
*3: '95-9 7 model s
Page
11-5 6
11-5 7
11-5 9
11-6 2
11-63
11-6 4
11-6 5
11-6 6
11-6 7
11-6 8
11-7 0
11-7 3
11-7 5
11-7 7
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Page
11-7 6
11-77
11-8 0
11-8 0
11-85
11-8 2
11-86
11-87
11-8 6
11-87
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