C Charts
Fig. 47 - Wiring Diagram for Chart C-4A Ignition System Check. VIN L:
CHART C4-A
C(3)1 IGNITION SYSTEM CHECK
(1 OF 2)
3.0L "N" SERIES
FUEL INJECTION (Port)
The C(3)1 ignition system uses a waste spark method of distribution. For example, when # 1 cylinder is on the compression stroke, the ignition module will trigger the # 1 and # 4 will be on the exhaust stroke, there will be very little energy needed to fire that plug so the remainder of the high voltage will be used to fire # 1 spark plug.
Fig. 46 - Chart C-4A Ignition System Check.:
1. If a plug wire is open, the other plug on that coil may still fire at idle. This tests the ability of the system to produce at least 25,000 volts.
2. No spark on one cylinder may be caused by an open plug wire or secondary winding. Therefore, both wires related to a coil and the secondary winding resistance should be checked. Resistance readings over the upper limit but not infinite will probably not cause a no start but may cause an engine miss under certain conditions.
3. This tests the triggering circuit in the ignition module. A blinking light indicates the module is triggering. The diagram above shows the control wire color for each coil. For example, if testing why # 1 plug did not fire, connect the test light between the blue feed wire and the yel/blk control wire.
4. A blinking test light at this point indicates the ECM is receiving the reference signal. The module will not send a reference signal to the ECM until it has received both a cam and crank signal.
5. A separate 10 amp, 12 V feed is used for the primary windings of the coils and this check will determine if the 12 volts is reaching the coils.
6. If 12 volts is reaching the ignition module on Terminal 'M' and the connection is good but 12 volts was not detected at the common feed blue wire at the coils, the module is open internally and must be replaced. If 12 volts is not reaching the module on Terminal 'M', the ignition feed wire and 25 amp fuse must be checked.
Fig. 048 - Chart C-4A Ignition System Check.:
CHART C4-A
C(3)1 IGNITION SYSTEM CHECK
(2 OF 2)
3.0L "N" SERIES
FUEL INJECTION (PORT)
For timing of spark plug firing, a dual crankshaft sensor "hall effect" switch is used. The cam signal part of this switch sends a signal to the ignition module when cylinder # 1 is on the compression stroke. This signal is used to start the correct sequence of coil firing. The engine will still run if the cam signal is lost while running, however, will not restart after shut down and a Code 41 will be stored if the cam signal was lost while running.
The crankshaft sensor also sends a signal to the ignition module an then to the ECM for reference RPM and crankshaft position. There are three windows in a plate which is mounted to the harmonic balancer. These windows pass by the sensor and as each window passes, the next coil is triggered.
1. This check will determine if the cam sensor signal is reaching the module. A steady high or low voltage on Terminal "B" indicates a faulty signal.
2. Probing Terminal "A and B" of sensor connector on the module side checks the voltage supply through the module, and connections at module.
2a. Checks for an open sensor ground circuit.
3. Checks for the 12 volt supply reaching the module on Terminal "P". If the 12 volts is present at "P" but was not present at the sensor connector Terminal "A" and all connections are good, the ignition module must be open internally.
4. In this step the "C" terminal is removed and a jumper wire installed to allow for access to signal wire being testing.
5. If the sensor is functioning properly and the wiring and connections are good, the ignition module is at fault. An open CKT 971 or 972 will cause a no start.
6. Probing Terminal "A" of sensor connector on the module side checks the sensor supply voltage through the module and connections at module.
6a. Checks for an open sensor ground circuit.
7. Checks voltage at Terminal "F" and "H" and if OK, the ignition module is bad.
8. If the sensor is functioning properly and the wiring and connections are good then the ignition module is faulty. An open CKT 430 will cause a no start but the ignition module will fire the plugs.