Circuit Description
The Secondary Ignition Check tests for faulty spark plugs, plug wires, or IC Module/Coils. This table requires the J 26792 spark tester (ST 125).
Test Description
Numbers below refer to the step numbers on the Diagnostic Table.
-
Ensure good DMM contact when measuring spark plug resistance. When manufactured the normal resistance for the spark plug is 900-2500 ohms but resistance growth up to 10K ohms is considered normal.
-
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.
-
The companion spark plug shares the same ignition coil with the spark being tested (1-4, 2-5, 6-7, 3-8).
-
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.
-
Ensure good DMM contact when measuring spark plug resistance. When manufactured the normal resistance for the spark plug is 900-2500 ohms but resistance growth up to 10K ohms is considered normal. A suspected ignition system miss may actually be a fuel system problem. Perform the Fuel System Diagnosis, if it has not yet been performed.
-
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 | Was the Powertrain OBD System Check performed? | -- | ||
2 | Key on and connect the scan tool. Are any PCM DTC(s) set? | -- | Go to applicable DTCs | |
3 | Perform Fuel Injector Balance Test using the scan tool and note cylinders with no engine speed or idle quality change. Were any cylinders noted? | -- | ||
4 | Were two companion cylinders noted? | -- | ||
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? | 7000 ohms (7K ohms) | ||
6 | Remove affected spark plug. Does spark look OK? | -- | ||
Measure resistance or affected spark plug. Does spark plug measure less than the specified value? | 10,000 ohms (10K ohms) | |||
Does spark jump tester gap? | -- | Go to Fuel System Diagnosis | ||
9 |
Does spark jump tester gap? | -- | ||
Does spark jump tester gap? | -- | |||
Switch affected coil with another coil and repeat the Fuel Injector Balance Test . Did the fault follow the affected coil? | -- | |||
12 |
Is ignition system arcing externally? | -- | ||
13 |
Does spark jump tester gap? | -- | ||
14 | 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? | 7000 ohms (7K ohms) | ||
15 | Remove affected spark plugs and check for wear, damage, or fouling. Do both plugs look OK? | -- | ||
Measure resistance of affected spark plugs. Do both spark plugs individually measure less than the specified value? | 10,000 ohms (10K ohms) | Go to Fuel System Diagnosis | ||
17 |
Does spark jump tester gap on all eight cylinders? | -- | Go to Fuel System Diagnosis | |
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? | -- | |||
19 |
Is either spark plug wire shorted to ground or more than the specified value? | 7000 ohms (7K ohms) | ||
20 | Remove affected spark plugs and check for wear, damage, or fouling. Do both plugs look OK? | -- | ||
21 | Measure resistance of affected spark plugs. Do both spark plugs individually measure less than the specified value? | 10,000 ohms (10K ohms) | ||
22 | Replace the spark plug wire. Refer to Spark Plug Replacement in Engine Electrical. Is the action complete? | -- | -- | |
23 | Replace the spark plug. Refer to Spark Plug Replacement in Engine Electrical. Is the action complete? | -- | -- | |
24 | Replace the affected spark plug. Refer to Spark Plug Replacement in Engine Electrical. Is the action complete? | -- | -- | |
25 | Replace the affected coil. Refer to Ignition Coil(s) Replacement . Is the action complete? | -- | -- | |
26 | Replace the IC Module. Refer to Ignition Control Module Replacement . Is the action complete? | -- | -- | |
27 | Repair the source of arcing. Is the action complete? | -- | -- | |
28 | Operate the vehicle within the conditions as noted by the customer. Was a driveability complaint noted? | -- | System OK |
