Honda Bmw 5 Service Manual

120-3 
Ignition System 
Warnings and cautions 
The ignition system  produces dangerous  high voltage. In ad- 
dition  the sensitive electronic components  can be damaged 
if 
proper  precautions are  not adhered  to. 
WARNING- 
* Do  not touch  or disconnect  any cables from the coils while 
the  engine  is running  or being 
cranked by  the  starter. 
The  ignition  system produces high voltages  that can be 
fatal.  Avoid  contact  with exposed  terminals. Use ex- 
treme caution  when working on  a...

I lgnition System 
Additional information about DTCs and engine management 
system electronic system  diagnosis is provided in 
OBD On- 
Board Diagnostics. 
Table  a. Engine  management  systems 
Year 
l~ngine I Engine type IDME svstem I - I - . . I 
Ignition system 
1997-1 998 
1997 
1998 
1999-2002 
4 All  engines  use a distributorless  ignition system with individ- 
ual  ignition  coils for  each cylinder.  There is no distributor  cap 
or ignition  rotor. 
4 Each coil is controlled  and monitored...

Lnition switch 
4 The positive (+) power supply  to the ignition coils  comes to 
the ignition  switch via an unloader  relay. When  the ignition 
switch  is turned on, the  relay closes,  to provide  voltage to the 
ignition  coils. The coils are  then actuated  at the  negative  side 
by  the engine control module. 
NOTE- 
Schematic diagrams shown are  for illustrative purposes  only. 
See  ELE  Electrical  Wiring Diagrams  for engine manage- 
ment specific wiring information. 
WARNING-  Do  not...

120-6 
lgnition System 
lgnition system, troubleshooting 
Troubleshooting ignition  system faults should begin with an 
interrogation  of the  On-Board Diagnostics (OBD 
II) system. 
The OBD 
II system detects ignition system misfire  and other 
related faults. When  faults are detected, the  OBD 
II system 
stores a Diagnostic Trouble  Code (DTC)  in the  Engine  Con- 
trol Module (ECM) along with other pertinent  fault information. 
4 In addition, the Malfunction Indicator Light (MIL) will  come on...

120-7 
Ignition System 
Spark plug electrode  gap /Too small /TOO big 
Table 
b. Ignition  secondary voltage diagnostics 
Secondary 
voltage low 
Fuel air  mixture 
I I Too lean 
Secondary 
voltage high 
Spark plug electrode 
Worniburnt 
4 The  illustration shows normal scope trace of spark  at idle. 
1. Start  of ignition  voltage peak 
2 Level of ignition  voltage 
3. Level of combustion  voltage 
4. Period of combustion 
5. Combustion curve characteristics 
6. Start  of decay process 
7. Termination...

I lgnition System 
4 Normal combustion  period at idle. 
4 Normal  oscilloscope  pattern for ignition  system  at idle. 
15. 15 
4 lgnition  voltage  peaks  at idle. 
1. Normal ignition  peaks. 
2. Downward peak (arrow) is shortened  (ignition  coil is 
defective). 
3. Downward  peak (arrow)  is missing completely  (ignition 
coil  is defective). 
4 Defective  ignition coil. 
1. Short spark  period. 
2. The spark voltage  line (arrow)  is very slight 
< Defective  ignition coil. 
1. Normal combustion...

< Ignition voltage peaks in response  to sudden  acceleration 
load: 
1. Normal ignition  pattern. Beginning  of dying out  pattern 
is  not  much higher than ignition  voltage peak. 
2. Beginning  of dying out pattern  considerably  higher  than 
ignition  voltage peak.  Fault  in injection  system: 
Lean  fuel mixture 
Defective  fuel injector 
Low compression  in cylinder 
-, :I 1- i : .... 1 ...,,,,. J ,,,.! ,.,. { .,., i .,,, 8 ,.,.$,.,! ,:,, ., xt * , *, ,, >* m2>2n,,,, 
Ignition firing  order...

.- 
ignition System 
Disabling ignition system 
The ignition system operates in a lethal voltage range and 
should be disabled  any time  engine  service  or repair  work is 
being  done that  requires the ignition to be switched on. 
The engine management  system can be disabled  by remov- 
ing the DME main relay. The  relay is located  in the electronics 
box (E-box)  in the left rear  of the engine 
compartment, be. 
neath the interior microfilter housing. 
CAUTION- Relay locations  may 
vary. Use...

Ignition System 
- Turn ignition on and  check for battery voltage, 
If  battery voltage is not present, 
checlt wire between  termi- 
nal 
15 and the unloader  relay. See ELE Electrical Wiring 
Diagrams. 
- Turn  ignition  off. 
Remove  coil and inspect coil housing  for hairline 
cracks or 
leaking casting material. Replace  any 
cracked or leaking coil. 
NOTE- 
A leaky coil may  indicate a faulty Engine Control Module 
(ECM).  Check ECM before installing a  new coil. 
CAUTION- 
Note  location  of...

120-1 2 
ignition System 
Crankshaftspeedsensor 
Crankshaft speed sensor, replacing (M52, M52 TU and 
M54 engines) 
4 Crankshaft speed sensor  for 6-cylinder engine is mounted in 
the left rear side  of the cylinder  block below the starter  (ar- 
row).  The sensor reads a toothed pulse wheel mounted to 
the end  of the crankshaft. 
- if the  Engine Control Module (ECM)  does not receive a signal 
from  the crankshaft speed  sensor during cranking,  the en- 
gine will not start. 
- If the  OBD II svstem...