Secondary Ignition Diagnosis. Oldsmobile Shelby Series 1 1999

For 1990-2009 cars

### 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.

1. Ensure good DMM contact when measuring spark plug resistance. When manufactured, the normal resistance for the spark plug is 3,000-8,000 ohms.

2. 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.

3. The companion spark plug shares the same ignition coil with the spark being tested (1-4, 2-5, 6-7, 3-8).

4. 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.

5. 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.

6. 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 | Go to Powertrain On Board Diagnostic (OBD) System Check
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
7 | 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

8

1. Ground companion spark plug lead for affected cylinder.
2. Install J 26792 spark tester.
3. Crank the engine and observe the spark plug tester.

Does spark jump tester gap?

--

Go to Fuel System Diagnosis

Go to Step 9

9

1. Ground affected spark plug lead.
2. Install the J 26792 spark tester on companion cylinder to the cylinder that was affected.
3. Crank the engine and observe the spark plug tester.

Does spark jump tester gap?

--

Go to Step 25

Go to Step 26

10

1. Ground one affected spark plug lead.
2. Install the J 26792 spark tester on companion cylinder of the grounded cylinder.
3. Crank the engine and observe the spark plug tester.

Does spark jump tester gap?

--

Go to Step 12

Go to Step 11

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

1. Reinstall all spark plugs and wires.
2. Start the engine and inspect for visible and audible arcing.

Is the ignition system arcing externally?

--

Go to Step 27

Go to Step 13

13

1. Ground the other affected spark plug lead.
2. Install the J 26792 spark tester on companion cylinder of the grounded cylinder.
3. Crank the engine and observe the spark plug tester.

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
16 | 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

1. Install the J 26792 spark tester on one spark plug wire and ground its companion cylinder.
2. Observe the spark plug tester with the engine idling.
3. Repeat the above test for each cylinder, being sure to ground the companion cylinders.

Does spark jump tester gap on all eight cylinders?

--

Go to Fuel System Diagnosis

Go to Step 18

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

1. Switch coils back.
2. Check the affected spark plug wire resistance to ground and resistance end to end.

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