Electronic Ignition (EI) System Diagnosis Introduction
When any condition is suspected to be caused by or related to the ignition control system, the first step in diagnosis should be to check for stored PCM DTCs. Diagnose all DTCs before further action is taken. If no DTCs are stored and the condition is still present, refer to the following:
| • | Ignition System Check. |
| • | Symptoms. |
| • | Engine Mechanical for base engine malfunctions. |
Electronic Ignition (EI) System Diagnosis Ignition System Check
Circuit Description
When any condition is suspected to be caused by or related to the Ignition System, the first step in diagnosis should be to Perform the Powertrain On Board Diagnostic (OBD) System Check .
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Was the Powertrain On Board Diagnostic (OBD) System Check performed? | -- | ||
2 | Are any PCM DTC(s) set? | -- | Refer to Powertrain Control Module Diagnosis | |
3 | Start the engine. Is there a no start or hard start condition? | -- | ||
4 |
Is voltage reading greater than the specified value? | 10 V | ||
5 | Drive vehicle and note any driveability symptoms. Is a miss, stumble, or hesitation noted? | -- | ||
6 | Are any other driveability symptoms noted? | -- | Refer to Symptoms table | |
7 |
If A problem is found repair as necessary. Refer to Repair Procedures in Electrical Diagnosis. Was a problem found? | -- | Refer to Symptoms table | |
8 | Operate the vehicle within the fail conditions as noted from the customer. Was a driveability complaint noted? | -- | System OK |
Electronic Ignition (EI) System Diagnosis Secondary Ignition Check
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 (ST125).
Test Description
Number(s) below refer to the step number(s) 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 Engine Cranks but Does Not Run performed? | -- | ||
2 | Key on and connect the scan tool. Are any PCM DTC(s) set? | -- | ||
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 | Reinstall all spark plugs and wires. Start engine and inspect for visible/audible arcing. 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 Engine Electrical. Is the action complete? | -- | -- | |
23 | Replace the spark plug. Refer to Engine Mechanical. Is the action complete? | -- | -- | |
24 | Replace the affected spark plug. Refer to Engine Mechanical. Is the action complete? | -- | -- | |
25 | Replace the affected coil. Refer to Ignition Coil . 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 |
