For 1990-2009 cars
Engine Controls Components
Ignition Control, Knock Sensors
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice

### Circuit Description

The Electronic Ignition system uses a waste spark method of spark distribution. In this type of ignition system, the ignition control module triggers the correct coil based on the sync signal received from the crankshaft position sensor, resulting in both spark plugs connected to the coil firing at the same time. The spark plug for the cylinder on the exhaust stroke requires a lower energy requirement to fire, leaving the remaining high voltage to fire the spark plug for the cylinder on the compression stroke.

During crank, the ignition control module monitors the CKP sync signal. The CKP sync signal is used to determine the correct cylinder pair to fire first. The CKP sync signal is used only by the ignition control module to initiate ignition coil firing sequence. It is not passed to the PCM. After the ignition control module processes the CKP sync signal, the ignition control module monitors the 18X CKP signal and sends 18X and 3X reference pulses to the PCM. When the PCM receives these pulses, the PCM will command all six injectors to allow a priming shot of fuel for all the cylinders. After the priming, the injectors are left OFF during the next six 3X reference pulses from the ignition control module. This allows each cylinder a chance to use the fuel from the priming shot. During this waiting period, the PCM receives a camshaft position signal pulse. The camshaft position signal allows the PCM to operate the injectors sequentially based on camshaft position. If the camshaft position signal is not present at start-up, the PCM will begin sequential fuel delivery with a 1 in 6 chance that fuel delivery is correct.

### Diagnostic Aids

An intermittent may be caused by a poor connection, rubbed through wire insulation or a wire broken inside the insulation. Check for the following items:

• | Poor connection or damaged harness.

| Inspect the PCM harness and connectors for improper mating, broken locks, improperly formed or damaged terminals, poor terminal to wire connection, and damaged harness.

• | Malfunctioning Engine Coolant Temperature Sensor.

| Using a scan tool, compare Engine Coolant Temperature with Intake Air Temperature on a completely cool engine. Engine Coolant Temperature should be within 10°C of Intake Air Temperature. If not, replace the ECT sensor.

• | Throttle Position Sensor.

| If the TP angle is over 80%, the PCM may operate in clear flood mode. The PCM will not allow fuel delivery while operating in clear flood mode.

### Test Description

Number(s) below refer to the step number(s) on the Diagnostic Table:

1. Determines if the ignition control module (ICM) is receiving the 18X CKP Reference signal. If the 18X CKP signal to the ICM is not present, there will be no RPM, spark, or fuel injector pulses.

2. Ensures that the ICM has the proper voltage supply and ground.

3. Verifies that the ICM is supplying the proper sensor feed voltage.

4. Test for the proper operation of the CKP Sync signal, ICM and related spark system components. Without the CKP Sync signal the ICM is unable to properly sequence the ignition coils.

5. If the 18X and CKP Sync signals to the ICM or the 18X and 3X reference signals to the ICM short together the vehicle will not start and run. However, there will be spark and fuel injector pulses.

6. This vehicle is equipped with a PCM which utilizes an Electrically Erasable Programmable Read Only Memory (EEPROM). When the PCM is replaced, the new PCM must be programmed.

#### Engine Cranks But Will Not Run

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | Go to Step 2 | Go to Powertrain On Board Diagnostic (OBD) System Check
2 | Important: Before proceeding with this table, ensure that the vehicle battery is fully charged. Important: If any DTCs are stored as failed since code clear, diagnose the DTCs before continuing with this table.

1. Inspect the fuses which supply ignition positive voltage to the following components:

• | Electronic ignition control module.

• | Fuel injectors.

2. If either fuse is open, locate and repair the short to ground in the affected ignition positive voltage circuit. Refer to Wiring Repairs .

Did you find and correct the condition?

--

Go to Powertrain On Board Diagnostic (OBD) System Check

Go to Step 3

3 |

1. Turn OFF the ignition.
2. Install a J 34730-1A Fuel Pressure Gauge.
3. Turn ON the ignition.
4. Observe the fuel pressure gauge.

Does the fuel pressure measure within the specified values and holding?

333-376 kPa (48-55 psi)

Go to Step 5

Go to Step 4

4 | Is any fuel pressure indicated? | -- | Go to Fuel System Pressure Test | Go to Fuel Pump Electrical Circuit Diagnosis
5 |

1. Turn OFF the ignition.
2. Remove the fuel pressure gauge.
3. Turn ON the ignition.
4. With a scan tool, observe the engine RPM while cranking the engine.

Does the scan tool indicate an engine RPM?

--

Go to Step 17

Go to Step 6

6 |

1. Turn OFF the ignition.
2. Disconnect the ignition control module (ICM).
3. Turn ON the ignition.
4. Connect a J 35616-200 Test Lamp between the ignition positive feed and ground circuits in the ICM connector.

Does the test lamp illuminate?

--

Go to Step 8

Go to Step 7

7 |

1. Leave the ICM disconnected.
2. Probe the ignition positive feed circuit at the ICM connector using a test lamp that is connected to a good ground.

Does the test lamp illuminate?

--

Go to Step 39

Go to Step 40

8 |

1. Turn OFF the ignition.
2. Reconnect the ICM.
3. Disconnect the 18X crankshaft position (CKP) sensor.
4. Turn ON the ignition.
5. Measure the voltage between the sensor feed and sensor ground circuits in the 18X sensor connector using a J 39200 Digital Multimeter.

Does the voltage measure near the specified value?

B+

Go to Step 9

Go to Step 11

9 | Measure the voltage between the sensor signal and sensor ground circuits in the 18X sensor connector using a DMM. Does the voltage measure within the specified values? | 6V-9V | Go to Step 10 | Go to Step 14
10 | Inspect for poor connections at the 18X sensor. Refer to Intermittents and Poor Connections Diagnosis . Did you find and correct the condition? | -- | Go to Powertrain On Board Diagnostic (OBD) System Check | Go to Step 41
11 | Measure the voltage on the sensor feed circuit at the 18X sensor connector using a DMM that is connected to a good ground. Does the voltage measure near the specified value? | B+ | Go to Step 12 | Go to Step 13
12 |

1. Turn OFF the ignition.
2. Leave the 18X sensor disconnected.
3. Disconnect the ICM.
4. Test the 18X sensor ground circuit for an open. Refer to Wiring Repairs .

Did you find and correct the condition?

--

Go to Powertrain On Board Diagnostic (OBD) System Check

Go to Step 38

13 |

1. Turn OFF the ignition.
2. Leave the 18X sensor disconnected.
3. Disconnect the ICM.
4. Test the 18X sensor feed circuit for an open or a short to ground. Refer to Wiring Repairs .

Did you find and correct the condition?

--

Go to the Powertrain On Board Diagnostic (OBD) System Check

Go to Step 41

14 |

1. Leave the DMM connected.
2. Turn OFF the ignition.
3. Disconnect the ICM.
4. Turn ON the ignition.

Does the DMM indicate any voltage?

--

Go to Step 15

Go to Step 16

15 | Locate and repair the short to voltage on the 18X sensor signal circuit. Refer to Wiring Repairs . Did you complete the repair? | -- | Go to Powertrain On Board Diagnostic (OBD) System Check | --
16 |

1. Turn OFF the ignition.
2. Disconnect the ICM.
3. Turn ON the ignition.
4. Test the 18X signal circuit for the following condition(s):

• | An open.

• | Short to ground or short to sensor ground.

Refer to Wiring Repairs .

Did you find and correct the condition?

--

Go to Powertrain On Board Diagnostic (OBD) System Check

Go to Step 38

17 |

1. Turn OFF the ignition.
2. Disconnect all fuel injectors.
3. Turn ON the ignition.
4. Observe the J 34730-2C Fuel Injector Test Lamp when installed in each injector connector.

Did the injector test lamp illuminate for any of the injectors?

--

Go to Step 18

Go to Step 19

18 |

1. Leave the fuel injectors disconnected.
2. Turn OFF the ignition.
3. Disconnect the PCM.
4. Turn ON the ignition.
5. Observe the injector test lamp when installed in the each injector connector.

Did the injector test lamp illuminated for any of the injectors?

--

Go to Step 43

Go to Step 46

19 |

1. Leave the fuel injectors disconnected.
2. Leave the injector test lamp installed in a injector connector.
3. Observe the injector test lamp while cranking the engine (repeat for each injector).

Did the injector test lamp blink for each injector?

--

Go to Step 24

Go to Step 20

20 | Did the injector test lamp blink for any of the injectors? | -- | Go to Step 21 | Go to Step 22
21 |

1. Turn OFF the ignition.
2. Leave the injectors disconnected.
3. Disconnect the PCM.
4. Test for an open in the fuel injector control circuit(s) associated with the injector test lamp that did not blink. Refer to Wiring Repairs .

Did you find and correct the condition?

--

Go to Powertrain On Board Diagnostic (OBD) System Check

Go to Step 44

22 |

1. Leave the fuel injectors disconnected.
2. Turn ON the ignition.
3. Probe the ignition positive feed circuit at each injector connector using a J 35616-200 Test Lamp that is connected to a good ground.

Does the test lamp illuminate?

--

Go to Step 24

Go to Step 23

23 | Locate and repair the open ignition positive feed circuit to the fuel injectors. Refer to Wiring Repairs . Did you complete the repair? | -- | Go to Powertrain On Board Diagnostic (OBD) System Check | --
24 |

1. Turn OFF the ignition.
2. Disconnect a spark plug wire from the spark plug.
3. Install J 26792 Spark Tester in the end of the spark plug wire.
4. Jumper the companion cylinder ignition wire to engine ground. The companion cylinder is the cylinder that shares the same ignition coil (i.e. 1/4, 2/5, 3/6).
5. Crank the engine while observing the spark tester. Spark should be observed.
6. Repeat the above test for each ignition wire, noting any cylinders that do not have spark.

Did you observe spark at all cylinders?

--

Go to Step 34

Go to Step 25

25 | Did you observe spark at any cylinder? | -- | Go to Step 30 | Go to Step 26
26 |

1. Turn OFF the ignition.
2. Disconnect the 18X sensor.
3. Turn ON the ignition.
4. Measure the voltage on the CKP Sync signal circuit using a J 39200 Digital Multimeter that is connected to a good ground.

Does the voltage measure near the specified value?

6V-9V

Go to Step 27

Go to Step 28

27 | Inspect for poor connections at the 18X sensor. Refer to Intermittents and Poor Connections Diagnosis and Connector Repairs . Did you find and correct the condition? | -- | Go to Powertrain On Board Diagnostic (OBD) System Check | Go to Step 41
28 |

1. Turn OFF the ignition.
2. Disconnect the ICM.
3. Turn ON the ignition.
4. Test the CKP Sync signal circuit for a short to voltage or a short to the 18X sensor feed circuit. Refer to Wiring Repairs

Did you find and correct the condition?

--

Go to Powertrain On Board Diagnostic (OBD) System Check

Go to Step 29

29 |

1. Turn OFF the ignition.
2. Disconnect the ICM.
3. Turn ON the ignition.
4. Test for the following circuit condition(s):

• | The CKP Sync signal circuit for a short to ground or a short to sensor ground.

• | An open CKP Sync signal circuit.

Refer to Wiring Repairs .

Did you find and correct the condition?

--

Go to Powertrain On Board Diagnostic (OBD) System Check

Go to Step 38

30 |

1. Remove and visually/physically inspect the ignition coil(s) and the ignition wires associated with the cylinders that did not have spark.
2. Ensure that the ignition wires, boots, coil(s), and coil towers are free of cracks and carbon tracking.

If a problem is found, replace the damaged ignition component(s). Refer to Ignition Coil Replacement .

Did you find and correct the condition?

--

Go to Powertrain On Board Diagnostic (OBD) System Check

Go to Step 31

31 | Measure the ignition coil secondary resistance using a DMM. If any resistance is outside the specified values, replace the malfunctioning ignition coil(s) as necessary. Refer to Ignition Coil Replacement . Did you find and correct the condition? | 5K-8K ohms (5000 - 8000 ohms) | Go to Powertrain On Board Diagnostic (OBD) System Check | Go to Step 32
32 | Measure the resistance of the ignition wires associated with the cylinders that did not have spark using a DMM. Replace the ignition wire(s) that measure more than the specified value. Refer to Spark Plug Wire Harness Replacement . Did you find and correct the condition? | 3280-4921 ohms/meter(1000-1500 ohms/ft) | Go to Powertrain On Board Diagnostic (OBD) System Check | Go to Step 33
33 |

1. Connect a J 35616-200 Test Lamp across the ignition module primary circuit (between the electronic ignition control module terminals) for the coil(s) associated with the cylinders which did not have spark.
2. Observe the test lamp while cranking the engine.

Does the test lamp blink continuously while the engine is cranking?

--

Go to Step 45

Go to Step 42

34 |

1. Remove the spark plugs from all of the cylinders. Refer to Spark Plug Replacement in Engine Electrical.
2. Visually/physically inspect the spark plug electrodes.

Did the spark plug inspection reveal excessive fouling?

--

Go to Base Engine Misfire Diagnosis in Engine Mechanical

Go to Step 35

35 | Test for the following condition(s):

• | A short between the 18X CKP and CKP Sync signal inputs to the ICM.

• | A short between the 18X and 3X reference signal inputs to the PCM.

• | Skewed ECT sensor.

• | Skewed or unresponsive MAP sensor.

If a problem is found, repair as necessary. Refer to Wiring Repairs .

Did you find and correct the condition?

--

Go to Powertrain On Board Diagnostic (OBD) System Check

Go to Step 36

36 | Test the fuel for contamination. Refer to Alcohol/Contaminants-in-Fuel Diagnosis . If a problem is found, clean the fuel system and correct the contaminated fuel conditions as necessary. Did you find and correct the condition? | -- | Go to Powertrain On Board Diagnostic (OBD) System Check | Go to Step 37
37 | Repair the engine mechanical problem. Refer to Base Engine Misfire Diagnosis in Engine Mechanical to diagnose the following condition(s):

• | Bent push rods.

• | Malfunctioning or incorrect camshaft.

• | Leaking or sticky valves or rings.

• | Excessive valve deposits.

• | Loose or worn rocker arms.

• | Weak valve springs.

• | Incorrect valve timing.

• | Leaking head gasket.

Did you complete the repair?

--

Go to Powertrain On Board Diagnostic (OBD) System Check

--

38 | Inspect for poor connections at the ICM. Refer to Intermittents and Poor Connections Diagnosis and Connector Repairs . Did you find and correct the condition? | -- | Go to Powertrain On Board Diagnostic (OBD) System Check | Go to Step 42
39 | Locate and repair the open in the ICM ground circuit. Refer to Wiring Repairs . Did you complete the repair? | -- | Go to Powertrain On Board Diagnostic (OBD) System Check | --
40 | Locate and repair the open in the ignition positive feed circuit to the ICM. Refer to Wiring Repairs . Did you complete the repair? | -- | Go to Powertrain On Board Diagnostic (OBD) System Check | --
41 | Replace the 18X CKP sensor. Refer to Crankshaft Position Sensor Replacement . Did you complete the replacement? | -- | Go to Powertrain On Board Diagnostic (OBD) System Check | --
42 | Replace the ICM. Refer to Ignition Control Module Replacement . Did you complete the replacement? | -- | Go to Powertrain On Board Diagnostic (OBD) System Check | --
43 | Locate and repair the short to ground in the fuel injector control circuit(s) associated with the injector test lamp(s) that stayed illuminated. Refer to Wiring Repairs . Did you complete the repair? | -- | Go to Powertrain On Board Diagnostic (OBD) System Check | --
44 | Inspect for poor connections at the PCM. Refer to Intermittents and Poor Connections Diagnosis and Connector Repairs . Did you find and correct the condition? | -- | Go to Powertrain On Board Diagnostic (OBD) System Check | Go to Step 46
45 | Replace the ignition coil(s) associated with the cylinder(s) that did not have spark. Refer to Ignition Coil Replacement . Did you complete the replacement? | -- | Go to Powertrain On Board Diagnostic (OBD) System Check | --
46 | Important: Replacement PCM must be reprogrammed. Refer to Powertrain Control Module Replacement/Programming . Replace the PCM. Did you complete the replacement? | -- | Go to Powertrain On Board Diagnostic (OBD) System Check | --