check engine light ACURA NSX 1991 Service Owner's Manual
[x] Cancel search | Manufacturer: ACURA, Model Year: 1991, Model line: NSX, Model: ACURA NSX 1991Pages: 1640, PDF Size: 60.48 MB
Page 1365 of 1640
Troubleshooting
TCS Indicator Light
Temporary Driving Conditions:
1. The TCS indicator light will come on and the control unit memorizes the Diagnostic Trouble Code (DTC) under cer-
tain temporary conditions:
2. If the TCS indicator light does not come back on after correcting the tire or tire pressure problem, the TCS system is
OK.
NOTE: Remove the ABS 2.3 (20 A) fuse for at least 3 seconds to clear the DTC from the TCS control unit memory.
TCS Diagnostic Trouble Code (DTC) Indication: 1. Stop the engine.
2. Turn the ignition switch on and confirm that the TCS indicator light comes on.
3. Turn the ignition switch off.
4. Connect the two terminals of the Service Check Connector with a jumper wire.
5. Turn the ignition switch on, but do not start the engine.6. Record the blinking frequency of the TCS indicator light. The blinking frequency indicates the DTC. Long blinks in- dicate the main code: short blinks indicate the sub-code.
7. Refer to the Troubleshooting Guide (page 19-84) for repair information. The spare tire is installed, or a tire of the improper size is installed.
The tire pressures are not correct.
SERVICE CHECK CONNECTOR (BLU)
SERVICE CHECK
CONNECTOR (BLU)
INDICATOR LIGHTProCarManuals.com
Page 1366 of 1640
The TCS control unit has three memory registers. When a problem occurs, the control unit stores the Diagnostic Trou-
ble Code (DTC) in the first memory register. If another problem occurs, or the same problem occurs again, the control
unit moves the first code to the next memory register and stores the second code in the first register. If there's a thirdproblem occurrence, the two existing code are moved up one register and the third code is stored in the first register.
If problems continue to occur, the oldest code is moved out of the last register and lost, and the most recent code is
stored in the first register. The TCS indicator light will not come on again after the engine starts unless another problem occurence is detected.
However, there will still be a code stored in the control unit's memory.
After the repair is completed, disconnect the jumper wire from the Service Check connector and remove the ABS 2.3
fuse (20 A) from the main relay box for at least 3 seconds to erase the control unit's memory. The control unit's memory is erased if the connector is disconnected from the control unit, or if the control unit is
removed from the car.
NOTE:
a: 2.0
sec.
c: 1.2
sec.
e: 0.3
sec.
g: 3.8
sec.
b: 0.5
sec.
d: 1.0
sec.
f: 2.5
sec.
Ignition
switch on
LIGHT
ON
LIGHT
OFF
First inspection Second inspection Third inspection First inspection
DTC 2-1 DTC 2 DTC 4-2 DTC 2-1
Engine start2nd cycle
ProCarManuals.com
Page 1393 of 1640
Ignition Timing Inspection and Setting
1. Start the engine and allow it to warm up (radiator
fan comes on).
2. Pull out the service check connector located under the middle of the dash. Connector the BLU andGRN/WHT terminals with a jumper wire (see sec-
tion 11).
3. Check the idle speed (see page 23-92).
4. Connect a timing light to the service loop; while the
engine idles, point the light toward the pointer on
the timing belt cover.
SERVICE LOOP
TIMING LIGHT
5. If necessary, adjust ignition timing to the following specifications:
Ignition Timing: 15° ±2° BTDC (RED mark)
Idle Speed (rpm):
NOTE: All electrical systems turned OFF. POINTER
RED MARK
CRANKSHAFT PULLEY
WHITE MARK
6. If necessary, adjust the ignition timing, adjust by turning the adjusting screw on the ignition timingadjuster in the control box.
Remove the control box cover. 7. Remove the jumper wire from the service check
connector.
8. After adjusting, reinstall the cover on the ignition timing adjuster with new rivets.ADJUSTING SCREW
To ADVANCE
To RETARD Reconnect the adjuster to the car, start the
engine, and turn the adjusting screw
counterclockwise to retard the timing, or
clockwise to advance it, as necessary.
CAUTION: Do not damage the adjuster when
removing the rivets. Remove the ignition timing adjuster from the
control box.
Drill the two rivets off with a 3/16 in. drill bit,
then separate the cover from the adjuster. 3-P CONNECTORCONTROL BOX
IGNITION TIMING
ADJUSTER
Remove the two screws from the control box
then disconnect the 3-P connector from the igni-
tion timing adjuster.ProCarManuals.com
Page 1477 of 1640
Troubleshooting
Troubleshooting Guide
NOTE: Across each row in the chart, the systems that could be sources of a symptom are ranked in the order they should be inspected starting with . Find the symptom in the left column, read across to the most likely source, then
refer to the page listed at the top of that column. If inspection shows the system is OK, try the next most likely system
,
etc.
* If codes other than those listed above are indicated, count the number of blinks again. If the indicator is in fact blinking these codes, substitute a known-good ECU and recheck. If the indication goes away, replace the original ECU. : If the Check Engine light is on while the engine is running, jump the service check connector. If no code is
displayed (Check Engine light stays on steady), the back-up system is in operation.
Substitute a known-good ECU and recheck. If the indication goes away, replace the original ECU.
PAGE
26
30, 32, 36
40
46
48
50
52
54
56
6-15ProCarManuals.com
Page 1479 of 1640
How to Read Flowcharts
A flowchart is designed to be used from start to final repair. It's like a map showing you the shortest distance. But beware: if you
go off the "map" anywhere but a "stop" symbol, you can easily get lost.
Describes the conditions or situation to start a troubleshooting flowchart.
(bold type)
Asks you to do something; perform a test, set up a condition, etc.
Asks you about the result of an action, then sends you in the appropriate troubleshooting direction.
The end of a series of actions and decisions, describes a final repair action and sometimes directs
(bold type) you to an earlier part of the flow to confirm your repair.
NOTE: The term "Intermittent Failure" is used in these charts. It simply means a system may have had a failure, but it checks
out OK through all your tests. You may need to road test the car to reproduce the failure or if the problem was a loose
connection, you may have unknowingly solved it while doing the tests. In any event, if the Check Engine light on the
dash does not come on, check for poor connections or loose wires at all connectors related to the circuit that you are
troubleshooting. Most of the troubleshooting flowcharts have you reset the ECU and try to duplicate the problem code. If the problem
is internittent and you can't duplicate the code, do not continue through the flowchart. To do so will only result in con-
fusion and, possibly, a needlessly replaced ECU. "Open" and "Short" are common electrical terms. An open is a break in a wire or at a connection. A short is an ac-
cidental connection of a wire to ground or to another wire. In simple electronics, this usually means something won't
work at all. In complex electronics (like ECUs), this can sometimes mean something works, but not the way it's sup-
posed to. If the electrical readings are not as specified when using the ECU test harness, check the test harness connections
before proceeding.ProCarManuals.com
Page 1480 of 1640
PGM-FI Control System
System Description
INPUTS ELECTRONIC CONTROL UNIT OUTPUTSCRANK/CYL SensorsMAP Sensor
TW Sensor
TA Sensor
Throttle Angle Sensor Oxygen SensorsEGR Valve Lift Sensor
Vehicle Speed Sensor
Ignition Timing Adjuster
Knock Sensers
A/T Fl Signals
TCS Signals
Starter Signal
Alternator FR Signal
Air Conditioning Signal
A/T Shift Position Signal M/T Neutral Switch Signal
M/T Clutch Switch Signal
Battery Voltage (IGN. 1)
Fuel Pump Terminal Voltage
VTEC Oil Pressure Switch
Signals
Injector Timing and Duration
Electronic Idle Control
Other Control Functions Ignition Timing Control
ECU Back-up Functions Injectors
Main Relay (Fuel Pump)
Fuel Pump Relay
Check Engine Light
EACV
A/C Compressor Clutch Relay
Igniter Unit
Purge Cut-Off Solenoid Valve
EGR Control Solenoid Valve
Chamber Volume Control Solenoid Valve
Radiator Fan Relay
Engine Compartment Fan Relay
VTEC Spool Valves
TCS Control Signals
Injector Tinning and Duration
The ECU contains memories for the basic discharge durations at various engine speeds and manifold pressures. The
basic discharge duration, after being read out from the memory, is further modified by signals sent from various sensors
to obtain the final discharge duration.
Electronic Air Control
Electronic Air Control Valve (EACV)
When the engine is cold, the A/C compressor is on, the transmission is in gear (A/T only) or the alternator is charging, the ECU
controls current to the EACV to maintain correct idle speed.
Ignition Timing Control
The ECU contains memories for basic ignition timing at various engine speeds and manifold pressures. Ignition timing
is also adjusted for coolant temperature.
A Knock Control System is also used. When detonation is detected by the knock sensor, the ignition timing is
retarded.
Other Control Functions
1. Starting Control
When the engine is started, the ECU provides a rich mixture.
2. Fuel Pump Control
When the ignition switch is initially turned on, the ECU supplies ground to the main relay which supplies current to
the fuel pump for two seconds to pressurize the fuel system.
When the engine is running, the ECU supplies ground to the mam relay which supplies current to the fuel pump.
When the engine is not running and the ignition is on, the ECU cuts ground to the main relay which cuts current
to the fuel pump.
Excellent engine performance is achieved through the use of VTEC (Variable Valve Timing and Lift Electronic Con-
trol System), intake manifold chamber control and discharge volume control of the fuel pump.
3. Fuel Cut-off Control During deceleration with the throttle valve closed, current to the injectors is cut off to improve fuel economy at
speeds over 1,500 rpm.
Fuel cut-off action also takes place
when
engine speed exceeds,
8,300
rpm, regardless
of the
position
of the
throttle valve, to protect the engine from over-revving.ProCarManuals.com
Page 1481 of 1640
4. A/C Compressor Clutch Relay
When the ECU receives a demand for cooling from the air conditioning system (compressor control unit), it delays
the compressor from being energized, and enriches the mixture to assure smooth transition to the A/C mode.
5. Purge Cut-off Solenoid Valve
When the coolant temperature is below 70 °C (158 °F), the ECU supplies a ground to the purge cut-off solenoid valve
which cuts vacuum to the purge control valve.
6. Chamber Volume Control Solenoid Valve (CVCSV)
When the engine rpm is below 4,800 rpm the CVCSV is activated by a signal from the ECU, intake air flows through
a smaller chamber, then high torque is delivered. At speeds higher than 4,800 rpm, both solenoid valves are deac-
tivated by the ECU, and intake air flows through the a larger chamber in order to increase airflow.
7. EGR Control Solenoid Valve (EGR CSV)
When the EGR is required for control of oxides of nitrogen (NOx) emissions, the ECU supplies ground to the EGR CSV
which supplies regulated vacuum to the EGR valve.
ECU Back-up Functions
1. Fail-Safe Function
When an abnormality occurs in a signal from a sensor, the ECU ignores that signal and assumes a pre-programmed
value that allows the engine to continue to run.
2. Back-up Function
When an abnormality occurs in the ECU itself, the injectors are controlled by a back-up circuit independent of the
system in order to permit minimal diving.
3. Self-diagnosis Function (Check Engine light)
When an abnormality occurs in a signal from a sensor, the ECU lights the Check Engine light and stores the failure
code in erasable memory. When the ignition is initially turned on, the ECU supplies ground for the Check Engine light
for two seconds.ProCarManuals.com
Page 1482 of 1640
PGM-FI Control System
Troubleshooting Flowchart
ECU
Check Engine light never comes
on (even for two seconds) after
ignition is turned on.
Is the oil pressure light on?
Turn the ignition switch OFF.
Inspect No. 5 fuse.
Is No. 5 fuse OK? Replace fuse.
Connect the ECU test harness
between the ECU and connector
(page 11-21).
Connect A13 terminal to body
ground.
Repair open in YEL between
No. 5 fuse and gauge assembly.
A13
Turn the ignition switch ON. Replace the light
bulb.
Repair open in BLU
wire between ECU
(A13) and gauge
assembly.
A23
A24 A26 B2
G101
Less than 1 V
Is Check Engine light on?
Measure voltage between body
ground and the following ter-
minals individually: A23, A24,
A26,
B2.
Is there less than 1V?
Repair open in wire
between ECU and in-
take manifold (G101)
that had more than 1V.
Substitute a known-good ECU and recheck. If symp-
tom/ indication goes away,
replace the original ECU.ProCarManuals.com
Page 1483 of 1640
Idle Control System
NOTE: Across each row in the chart, the sub systems that could be sources of a symptom are ranked in the order they should
be inspected, starting with . Find the symptom in the left column, read across to the most likely source, then refer to
the page listed at the top of that column. If inspection shows the system is OK, try the next system , etc.
If the idle speed is out of specification and the Check Engine light does not blink CODE 14, go to inspection described
on page 11-70.
PAGE
86
70
72
74
76
78
80
82
83 *
System Troubleshooting GuideProCarManuals.com
Page 1486 of 1640
1. When the idle speed is out of specification and the Check Engine light does not blink CODE 14, check the following
items:Adjust the idle speed (page 11- 84)
Air conditioning signal (page 11-72)
Alternator FR signal (page 11-74)
A/T shift position signal (page 11-76) M/T neutral switch signal (page 11-78)
M/T clutch switch signal (page 11- 80)
Starter switch signal (page 11- 82)
Fast idle valve (page 11- 83)
Hoses and connections
EACV and its mounting O-rings
2. If the above items are normal, substitute a known-good EACV and readjust the idle speed (page 11- 84).
If the
idle
speed
still
cannot
be
adjusted
to
specification (and
the
Check Engine
light
does
not
blink
CODE
14)
after
EACV replacement, substitute a known-good ECU and recheck. If symptom goes away, replace the original ECU.ProCarManuals.com