How to diagnose LS2 Coils
Did you perform the Diagnostic System Check-Engine Controls?
--
YES:Go to Step 2
NO:Go to Diagnostic System Check - Engine Controls
2
Crank the engine.
Observe the engine speed parameter with a scan tool.
Does the scan tool display engine RPM?
--
YES:Go to Step 3
NO:Go to Step 13
3
Is DTC P0335, P0336, or P0351-P0358 also set?
--
YES:Go to Diagnostic Trouble Code (DTC) List
NO:Go to Step 4
4
Idle the engine.
Observe the misfire current counters on the scan tool.
Does the scan tool display any misfire current counters incrementing?
--
YES:Go to Step 5
NO:Go to Intermittent Conditions
5
Turn OFF the ignition.
Remove the fuel pump relay.
Test for spark at each affected cylinder with the J 26792 Spark Tester.
Do you have bright blue spark on the cylinders?
--
YES:Go to Step 6
NO:Go to Step 7
6
Remove the spark plugs.
Inspect the spark plugs for any abnormal conditions or damage. Refer to Spark Plug Inspection .
Are the spark plugs in good condition?
--
YES:System OK
NO:Go to Step 22
7
Measure the spark plug wire resistance. Refer to Spark Plug Wire Inspection .
Is the resistance more than the specified value?
700 ohms/ft
Go to Step 23
Go to Step 8
8
Turn OFF the ignition.
Disconnect the affected ignition coil.
Turn ON the ignition, with the engine OFF.
Probe the ignition voltage circuit of the affected ignition coil with a test lamp that is connected to a good ground. Refer to Probing Electrical Connectors in Wiring Systems.
Does the test lamp illuminate?
--
YES:Go to Step 9
NO: Go to Step 19
9
Probe the ignition voltage circuit at the affected ignition coil with a test lamp that is connected to the ground circuit of the affected ignition coil. Refer to Probing Electrical Connectors in Wiring Systems.
Does the test lamp illuminate?
--
YES:Go to Step 10
NO:Go to Step 20
10
Probe the ignition voltage circuit at the affected ignition coil with a test lamp that is connected to the low reference circuit of the affected ignition coil. Refer to Probing Electrical Connectors in Wiring Systems.
Does the test lamp illuminate?
--
YES:Go to Step 11
NO:Go to Step 15
11
Measure the resistance of the ignition voltage circuit of the affected ignition coil from the fuse that supplies ignition voltage to the affected ignition coil to the harness connector of the affected ignition coil.
Is the resistance less than the specified value?
3 ohms
YES:Go to Step 12
NO:Go to Step 19
12
Measure the resistance of the ground circuit of the affected ignition coil from the harness connector of the affected ignition coil to a good ground.
Is the resistance less than the specified value?
3 ohms
YES:Go to Step 17
NO:Go to Step 20
13
Turn ON the ignition, with the engine OFF.
Disconnect the crankshaft position (CKP) sensor.
Measure the voltage from the CKP sensor 12-volt reference circuit to a good ground with the DMM.
Compare the measured voltage with the system voltage.
Is the difference in the voltage more than the specified value?
0.5 V
YES:Go to Step 14
NO:Go to Step 16
14
Test for a short to ground in the CKP 12-volt reference circuit or the camshaft position (CMP) sensor 12-volt reference circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
--
YES:Go to Step 26
NO:Go to Step 18
15
Test the low reference circuit of the ignition coil for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
--
YES:Go to Step 26
NO:Go to Step 18
16
Test for shorted terminals and poor connections at the CKP sensor. Refer to Testing for Intermittent and Poor Connections and Connector Repairs in Wiring Systems.
Did you find and correct the condition?
--
YES:Go to Step 26
NO:Go to Step 21
17
Test for an intermittent and for a poor connections at the ignition coil. Refer to Testing for Intermittent and Poor Connections and Connector Repairs in Wiring Systems.
Did you find and correct the condition?
--
YES:Go to Step 26
NO:Go to Step 24
18
Test for shorted terminals and for poor connections at the powertrain control module (PCM). Refer to Testing for Intermittent and Poor Connections and Connector Repairs in Wiring Systems.
Did you find and correct the condition?
--
YES:Go to Step 26
NO:Go to Step 25
19
Repair the ignition voltage circuit of the affected ignition coil for one of the following conditions:
An open
High resistance
A short to ground
Refer to Wiring Repairs in Wiring Systems.
Did you complete the repair?
--
YES:Go to Step 26
--
20
Repair the ground circuit of the affected ignition coil for one of the following conditions:
An open
High resistance
Refer to Wiring Repairs in Wiring Systems.
Did you complete the repair?
--
YES:Go to Step 26
--
21
Replace the CKP sensor. Refer to Crankshaft Position (CKP) Sensor Replacement .
Did you complete the replacement?
--
YES:Go to Step 26
--
22
Replace the spark plug. Refer to Spark Plug Replacement .
Did you complete the replacement?
--
YES:Go to Step 26
--
23
Replace the spark plug wire. Refer to Spark Plug Wire Replacement .
Did you complete the replacement?
--
YES:Go to Step 26
--
24
Replace the ignition coil. Refer to Ignition Coil(s) Replacement .
Did you complete the replacement?
--
YES:Go to Step 26
--
25
Replace the PCM. Refer to Powertrain Control Module (PCM) Replacement .
Did you complete the replacement?
--
YES:Go to Step 26
--
26
Turn OFF the engine for 30 seconds.
Start the engine and operate the vehicle.
Observe the vehicle performance and driveability.
Does the vehicle operate normally?
--
YES:System OK
NO:Go to Step 3
--
YES:Go to Step 2
NO:Go to Diagnostic System Check - Engine Controls
2
Crank the engine.
Observe the engine speed parameter with a scan tool.
Does the scan tool display engine RPM?
--
YES:Go to Step 3
NO:Go to Step 13
3
Is DTC P0335, P0336, or P0351-P0358 also set?
--
YES:Go to Diagnostic Trouble Code (DTC) List
NO:Go to Step 4
4
Idle the engine.
Observe the misfire current counters on the scan tool.
Does the scan tool display any misfire current counters incrementing?
--
YES:Go to Step 5
NO:Go to Intermittent Conditions
5
Turn OFF the ignition.
Remove the fuel pump relay.
Test for spark at each affected cylinder with the J 26792 Spark Tester.
Do you have bright blue spark on the cylinders?
--
YES:Go to Step 6
NO:Go to Step 7
6
Remove the spark plugs.
Inspect the spark plugs for any abnormal conditions or damage. Refer to Spark Plug Inspection .
Are the spark plugs in good condition?
--
YES:System OK
NO:Go to Step 22
7
Measure the spark plug wire resistance. Refer to Spark Plug Wire Inspection .
Is the resistance more than the specified value?
700 ohms/ft
Go to Step 23
Go to Step 8
8
Turn OFF the ignition.
Disconnect the affected ignition coil.
Turn ON the ignition, with the engine OFF.
Probe the ignition voltage circuit of the affected ignition coil with a test lamp that is connected to a good ground. Refer to Probing Electrical Connectors in Wiring Systems.
Does the test lamp illuminate?
--
YES:Go to Step 9
NO: Go to Step 19
9
Probe the ignition voltage circuit at the affected ignition coil with a test lamp that is connected to the ground circuit of the affected ignition coil. Refer to Probing Electrical Connectors in Wiring Systems.
Does the test lamp illuminate?
--
YES:Go to Step 10
NO:Go to Step 20
10
Probe the ignition voltage circuit at the affected ignition coil with a test lamp that is connected to the low reference circuit of the affected ignition coil. Refer to Probing Electrical Connectors in Wiring Systems.
Does the test lamp illuminate?
--
YES:Go to Step 11
NO:Go to Step 15
11
Measure the resistance of the ignition voltage circuit of the affected ignition coil from the fuse that supplies ignition voltage to the affected ignition coil to the harness connector of the affected ignition coil.
Is the resistance less than the specified value?
3 ohms
YES:Go to Step 12
NO:Go to Step 19
12
Measure the resistance of the ground circuit of the affected ignition coil from the harness connector of the affected ignition coil to a good ground.
Is the resistance less than the specified value?
3 ohms
YES:Go to Step 17
NO:Go to Step 20
13
Turn ON the ignition, with the engine OFF.
Disconnect the crankshaft position (CKP) sensor.
Measure the voltage from the CKP sensor 12-volt reference circuit to a good ground with the DMM.
Compare the measured voltage with the system voltage.
Is the difference in the voltage more than the specified value?
0.5 V
YES:Go to Step 14
NO:Go to Step 16
14
Test for a short to ground in the CKP 12-volt reference circuit or the camshaft position (CMP) sensor 12-volt reference circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
--
YES:Go to Step 26
NO:Go to Step 18
15
Test the low reference circuit of the ignition coil for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
--
YES:Go to Step 26
NO:Go to Step 18
16
Test for shorted terminals and poor connections at the CKP sensor. Refer to Testing for Intermittent and Poor Connections and Connector Repairs in Wiring Systems.
Did you find and correct the condition?
--
YES:Go to Step 26
NO:Go to Step 21
17
Test for an intermittent and for a poor connections at the ignition coil. Refer to Testing for Intermittent and Poor Connections and Connector Repairs in Wiring Systems.
Did you find and correct the condition?
--
YES:Go to Step 26
NO:Go to Step 24
18
Test for shorted terminals and for poor connections at the powertrain control module (PCM). Refer to Testing for Intermittent and Poor Connections and Connector Repairs in Wiring Systems.
Did you find and correct the condition?
--
YES:Go to Step 26
NO:Go to Step 25
19
Repair the ignition voltage circuit of the affected ignition coil for one of the following conditions:
An open
High resistance
A short to ground
Refer to Wiring Repairs in Wiring Systems.
Did you complete the repair?
--
YES:Go to Step 26
--
20
Repair the ground circuit of the affected ignition coil for one of the following conditions:
An open
High resistance
Refer to Wiring Repairs in Wiring Systems.
Did you complete the repair?
--
YES:Go to Step 26
--
21
Replace the CKP sensor. Refer to Crankshaft Position (CKP) Sensor Replacement .
Did you complete the replacement?
--
YES:Go to Step 26
--
22
Replace the spark plug. Refer to Spark Plug Replacement .
Did you complete the replacement?
--
YES:Go to Step 26
--
23
Replace the spark plug wire. Refer to Spark Plug Wire Replacement .
Did you complete the replacement?
--
YES:Go to Step 26
--
24
Replace the ignition coil. Refer to Ignition Coil(s) Replacement .
Did you complete the replacement?
--
YES:Go to Step 26
--
25
Replace the PCM. Refer to Powertrain Control Module (PCM) Replacement .
Did you complete the replacement?
--
YES:Go to Step 26
--
26
Turn OFF the engine for 30 seconds.
Start the engine and operate the vehicle.
Observe the vehicle performance and driveability.
Does the vehicle operate normally?
--
YES:System OK
NO:Go to Step 3
TECH Apprentice
Joined: Oct 2005
Posts: 320
Likes: 0
From: Norwalk, CT
A simple test would be to see which cylinder is misfiring. Then swap a coil from a good
cylinder with the suspected bad one and see if misfire has changed cylinders (Do this using a scan tool.) If misfire changed cylinders-bad coil. If not, possible wiring problem....
cylinder with the suspected bad one and see if misfire has changed cylinders (Do this using a scan tool.) If misfire changed cylinders-bad coil. If not, possible wiring problem....
TECH Addict
Joined: Nov 2001
Posts: 2,003
Likes: 0
From: Live Oak, FL - in the woods where the creatures lurk.
Same way you diagnose any coil? 
If you just want to know if it's firing -at all- pull the plug and look at it, or get a spare and hook to the wire and ground the electrode and have someone crank the engine while you check if the plug is firing.
For an intermittent condition, put a fresh plug in and use a known good plug wire and check misfire counts, as suggested. If the harness connections have been r&r 'd mucho times check for continuity there, bad connection, etc.
HTH.
If you just want to know if it's firing -at all- pull the plug and look at it, or get a spare and hook to the wire and ground the electrode and have someone crank the engine while you check if the plug is firing.
For an intermittent condition, put a fresh plug in and use a known good plug wire and check misfire counts, as suggested. If the harness connections have been r&r 'd mucho times check for continuity there, bad connection, etc.
HTH.
