Circuit Description
The secondary ignition check tests for faulty spark plugs, plug wires, ignition control modules (ICM), or ignition control coils. This table requires the J 26792 spark tester (ST 125).
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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Ensure good DMM contact when measuring spark plug resistance. When manufactured, the normal resistance for the spark plug is 3,000-8,000 ohms.
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The J 26792 spark tester (ST 125) presents a more difficult load on the secondary ignition than a normal spark plug. If a miss, stumble, or hesitation is being caused by a spark plug not firing, the spark tester should also not fire.
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The companion spark plug shares the same ignition coil with the spark being tested (1-4, 2-5, 6-7, 3-8).
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If the no spark condition follows the suspected coil, that coil is faulty. Otherwise, the ignition module is the cause of no spark. This test could also be performed by substituting a known good coil for the one causing the no spark condition.
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Ensure good DMM contact when measuring spark plug resistance. When manufactured, the normal resistance for the spark plug is 3,000-8,000 ohms. A suspected ignition system miss may actually be a fuel system problem. Perform the Fuel System Check, if it has not yet been performed.
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If the no spark condition follows the suspected coil, that coil is faulty. This test could also be performed by substituting a known good coil for the one causing the no spark condition.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | Go to Step 2 | |
2 | Key ON and connect the scan tool. Are any PCM DTCs set? | -- | Go to those DTCs first | Go to Step 3 |
3 | Perform the Injector Balance Check using the scan tool and record the cylinders with no engine speed or idle quality change. Were any low or non-functioning cylinders observed? | -- | Go to Step 4 | Go to Step 17 |
4 | Were two companion cylinders, 1 and 4, 2 and 5, 6 and 7, or 3 and 8, observed? | -- | Go to Step 10 | Go to Step 5 |
5 | Check affected spark plug wire resistance to ground and resistance end to end. Is spark plug wire shorted to ground or more than the specified value? | 15,000 ohms | Go to Step 22 | Go to Step 6 |
6 | Remove affected spark plug. Does spark plug look OK? | -- | Go to Step 7 | Go to Step 23 |
Measure resistance or affected spark plug. Does spark plug measure less than the specified value? | 15,000 ohms | Go to Step 8 | Go to Step 23 | |
Does spark jump tester gap? | -- | Go to Fuel System Diagnosis | Go to Step 9 | |
9 |
Does spark jump tester gap? | -- | Go to Step 25 | Go to Step 26 |
Does spark jump tester gap? | -- | Go to Step 12 | Go to Step 11 | |
Switch affected coil with another coil and repeat the Injector Balance Check using the scan tool. Did the fault follow the affected coil? | -- | Go to Step 25 | Go to Step 26 | |
12 |
Is the ignition system arcing externally? | -- | Go to Step 27 | Go to Step 13 |
13 |
Does spark jump tester gap? | -- | Go to Step 14 | Go to Step 25 |
14 | Check affected spark plug wire resistance to ground and resistance end to end. Is the spark plug wire shorted to ground or more than the specified value? | 15,000 ohms | Go to Step 22 | Go to Step 15 |
15 | Remove affected spark plugs and check for wear, damage, or fouling. Do both plugs look OK? | -- | Go to Step 16 | Go to Step 24 |
Measure resistance of affected spark plugs. Do both spark plugs individually measure less than the specified value? | 15,000 ohms | Go to Fuel System Diagnosis | Go to Step 24 | |
17 |
Does spark jump tester gap on all eight cylinders? | -- | Go to Fuel System Diagnosis | Go to Step 18 |
Switch affected coil with another coil and repeat the spark plug tester test on all four cylinders of switched coils. Did the fault follow the affected coil? | -- | Go to Step 25 | Go to Step 19 | |
19 |
Is either spark plug wire shorted to ground or more than the specified value? | 15,000 ohms | Go to Step 22 | Go to Step 20 |
20 | Remove affected spark plugs and check for wear, damage, or fouling. Do both plugs look OK? | -- | Go to Step 21 | Go to Step 24 |
21 | Measure resistance of affected spark plugs. Do both spark plugs individually measure less than the specified value? | 15,000 ohms | Go to Step 26 | Go to Step 24 |
22 | Replace the spark plug wire. Is the action complete? | -- | Go to Step 28 | -- |
23 | Replace the spark plug. Is the action complete? | -- | Go to Step 28 | -- |
24 | Replace the affected spark plug. Is the action complete? | -- | Go to Step 28 | -- |
25 | Replace the affected coil. Is the action complete? | -- | Go to Step 28 | -- |
26 | Replace the ICM. Is the action complete? | -- | Go to Step 28 | -- |
27 | Repair the source of arcing. Is the action complete? | -- | Go to Step 28 | -- |
28 | Select the Capture Info option and the Review Info option using the scan tool. Does the scan tool display any DTCs that you have not diagnosed? | -- | Go to the applicable DTC table | System OK |
