1995 ACURA TL change time

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

Brake Booster

Inspection

Functional Test

1. With the engine stopped, depress the brake pedal

several times to deplete the vacuum reservoir, then

depress the pedal hard and hold it for 15 seconds. If

the pedal sinks, either the master cylinder is

bypassing internally, or the brake system (master

cylinder, lines, modulator, proportioning valve, or

caliper) is leaking.

2. Start the engine with the pedal depressed. If the

pedal sinks slightly, the vacuum booster is operat-

ing normally. If the pedal height does not vary, the

booster or check valve is faulty.

3. With the engine running, depress the brake pedal

lightly. Apply just enough pressure to hold back

automatic transmission creep. If the brake pedal

sinks more than 25 mm (1.0 in.) in three minutes, the

master cylinder is faulty. A slight change in pedal

height when the A/C compressor cycles on and off if

normal. (The A/C compressor load changes the vac-

uum available to the booster.)

Leak Test

1. Depress the brake pedal with the engine running,

then stop the engine. If the pedal height does not

vary while depressed for 30 seconds, the vacuum

booster is OK. If the pedal rises, the booster is faulty.

2. With the engine stopped, depress the brake pedal

several times using normal pressure. When the

pedal is first depressed, it should be low. On consec-

utive applications, the pedal height should gradually

rise. If the pedal position does not vary, check the

booster check valve.ProCarManuals.com

Wheel Speed and Modulator Control

When the wheel speed drops sharply below the vehicle speed, the inlet valve closes to retain the caliper fluid pressure.

When the wheel speed drops further, the outlet valve opens momentarily to reduce the caliper fluid pressure. The pump

motor starts at this time.

As the wheel speed is restored, the inlet valve opens momentarily to increase the caliper fluid pressure.

Wheel Sensor

The wheel sensors are the magnetic contactless type.

As the gear pulser teeth rotate past the wheel sensor's magnetic coil, AC current is generated. The AC frequency changes

in accordance with the wheel speed. The ABS control unit detects the wheel sensor signal frequency and thereby detects

the wheel speed.

There are four wheel sensors, one for each wheel.

The gear pulser has 50 teeth.

GEAR PULSER

WHEEL SENSORProCarManuals.com