Circuit Description
The electronic ignition (EI) system uses a waste spark method of spark distribution. In this type of EI system, the crankshaft position (CKP) sensor is mounted to the oil pump near a slotted wheel that is a part of the crankshaft pulley. The CKP sensor sends reference pulses to the engine control module (ECM). The ECM then triggers the EI system ignition coil. Once the ECM triggers the EI system ignition coil, both of the connected spark plugs fire at the same time. One cylinder is on its compression stroke at the same time that the other is on the exhaust stroke, resulting in lower energy needed to fire the spark plug in the cylinder on its exhaust stroke.
This leaves the remainder of the high voltage to be used to fire the spark plug in the cylinder on its compression stroke. Since the CKP sensor is in a fixed position, timing adjustments are not possible or needed.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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It is important to check for the presence of spark to all of the cylinders to isolate the problem to either EI system ignition coil inputs or outputs.
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In inspecting the ECM outputs for the electronic spark timing signal, it is recommended to use an oscilloscope to view the varying voltage signals. In measuring these outputs with a voltmeter, intermittent errors may occur that cannot be seen by a voltmeter.
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After confirming ECM inputs for the electronic spark timing to the EI system ignition coil are OK, it can be determined that a faulty EI system ignition coil is at fault.
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After confirming proper CKP sensor inputs to the ECM and no wiring problems are present, it can be determined that the ECM is at fault.
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This step, along with step 25, checks for battery voltage and a ground to the EI system ignition coil.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
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Caution: When working on the engine ignition system, use only electrically insulated pliers when handling ignition wires with the engine running. The ignition system produces high voltage while the engine is running and could cause serious personal injury if not handled properly. | ||||
1 |
Did you find and correct the condition? | -- | System OK | Go to Step 2 |
Test for the presence of spark from all of the ignition wires while cranking the engine. Is spark present from all of the ignition wires? | -- | System OK | Go to Step 3 | |
3 |
Is spark present from all of the ignition wires? | 30,000 ohms | System OK | Go to Step 4 |
4 | Is spark present from at least one of the ignition wires, but not all of the ignition wires? | -- | Go to Step 5 | Go to Step 12 |
Does the voltage fluctuate within the specified range? | 0.2-2 V | Go to Step 6 | Go to Step 7 | |
While cranking the engine, measure the voltage at the EI system ignition coil connector terminal A. Does the voltage fluctuate within the specified range? | 0.2-2 V | Go to Step 10 | Go to Step 8 | |
7 | Inspect for an open in the wire from the EI system ignition coil connector terminal C to the engine control module (ECM) connector terminal M35 or M51. Is a repair necessary? | -- | Go to Step 9 | Go to Step 11 |
8 | Inspect for an open in the wire from the EI system ignition coil connector terminal A to the ECM connector terminal M1 or M33. Is a repair necessary? | -- | Go to Step 9 | Go to Step 11 |
9 |
Is spark present from all of the ignition wires? | -- | System OK | -- |
10 |
Is spark present from all of the ignition wires? | -- | System OK | -- |
Is spark present from all of the ignition wires? | -- | System OK | -- | |
12 |
Is the resistance within the specified range? | 400-600 ohms | Go to Step 13 | Go to Step 28 |
13 |
Is the resistance equal to the specified value? | ∞ | Go to Step 14 | Go to Step 28 |
14 |
Is the voltage within the specified range? | 1.3-1.5 V (2.4-2.7 V) | Go to Step 20 | Go to Step 15 |
15 | Measure the voltage between the CKP sensor connector terminal 1 and ground. Is the voltage within the specified range? | 1.3-1.5 V (2.4-2.7 V) | Go to Step 17 | Go to Step 16 |
16 | Inspect the wire between the CKP sensor connector terminal 1 and the ECM connector terminal M21 for an open or short. Is a repair necessary? | -- | Go to Step 18 | Go to Step 11 |
17 | Inspect the wire between the CKP sensor connector terminal 3 and ground for an open or short. Is a repair necessary? | -- | Go to Step 19 | Go to Step 11 |
18 | Repair the wire between the CKP sensor connector terminal 1 and the ECM connector terminal M21. Did you complete the repair? | -- | System OK | -- |
19 | Repair the wire between the CKP sensor connector terminal 3 and ground. Did you complete the repair? | -- | System OK | -- |
20 |
Is the voltage within the specified range? | 1.3-1.5 V (2.4-2.7 V) | Go to Step 24 | Go to Step 21 |
21 | Measure the voltage between the CKP sensor connector terminal 2 and ground. Is the voltage within the specified range? | 1.3-1.5 V (2.4-2.7 V) | Go to Step 17 | Go to Step 22 |
22 | Inspect the wire between the CKP sensor connector terminal 2 and the ECM connector terminal M5 for an open or short. Is a repair necessary? | -- | Go to Step 23 | Go to Step 11 |
23 | Repair the wire between the CKP sensor connector terminal 2 and the ECM connector terminal M5. Did you complete the repair? | -- | System OK | -- |
Is the test light ON? | -- | Go to Step 25 | Go to Step 26 | |
25 | Connect a test light between the EI system ignition coil connector terminal B and battery positive. Is the test light ON? | -- | Go to Step 5 | Go to Step 27 |
26 | Inspect for an open or short to ground in the wiring between the EI system ignition coil connector, terminal B, and the ignition switch. Is a repair necessary? | -- | Go to Step 29 | -- |
27 | Repair the wire between the EI system ignition coil connector terminal C and ground. Did you complete the repair? | -- | System OK | -- |
28 |
Did you complete the replacement? | -- | System OK | -- |
29 | Replace the fuse F7 or repair the open in the wiring between the EI system ignition coil connector terminal B and the ignition switch. Did you complete the repair? | -- | System OK | -- |
