Refer to
Ignition Control Module, CMP and CKP
Refer to
Fuel Injectors
.
The Electronic Ignition system uses a waste spark method of spark distribution. The ignition control module (ICM) determines the correct coil sequence based on the CKP sync signal received from the crankshaft position sensor. Two spark plugs connected to the coil fire at the same time. The cylinder on the compression stroke (event cylinder) uses most of the coil's available voltage to fire the spark plug. The cylinder on the exhaust stroke (waste cylinder) uses the remaining coil energy to fire the spark plug.
During crank, the ICM monitors the 18X CKP and CKP sync signals. The ICM uses CKP sync signal to determine the correct cylinder pair to fire first. Only the ICM uses the CKP sync signal. The ICM does not pass the CKP signal to the PCM. While the ICM processes the CKP sync signal, the ICM also monitors the 18X CKP signal. The ICM uses the 18X signal for crankshaft position information and to generate 3X reference pulses. The ICM sends the 18X and 3X reference pulses to the PCM. When the PCM receives these pulses, the PCM energizes all six injectors to allow a priming shot of fuel for the cylinders. After priming the cylinders, the PCM shuts the injectors OFF for the next six, 3X reference pulses. This allows each cylinder a chance to use the fuel from the priming shot. During this waiting period, the PCM receives a camshaft position (CMP) signal pulse. The CMP signal allows the PCM to calculate true sequential fuel injection. If a loss of the CMP signal occur during start-up, the PCM still operates the fuel injectors sequentially. However, fuel injection occurs with a 1 in 6 chance that the injector sequencing is correct.
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. |
• | Faulty 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. Refer to Engine Coolant Temperature Sensor Replacement . |
The numbers below refer to the step numbers on the Diagnostic Table:
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 are no RPM, spark, or fuel injector pulses.
Ensures that the ICM has the proper voltage supply and ground.
Verifies that the ICM is supplying the proper sensor feed voltage.
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.
If the 18X and CKP sync signals to the ICM or the 18X and 3X reference signals to the ICM short together the vehicle does not start and run. However, there are spark and fuel injector pulses.
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.
Step | Action | Value(s) | Yes | No | ||||||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1 | Did you complete the Powertrain On-Board Diagnostic (OBD) System Check? | -- | ||||||||||||||||||
2 |
Important: Before proceeding with this diagnostic, ensure that the vehicle's battery is fully charged. Important: If any DTCs are stored as Failed Since Code Clear, diagnose the DTCs before continuing with this table.
Was a problem found? | -- | ||||||||||||||||||
3 |
Is the fuel pressure holding within the specified range? | 333-376 kPa (48-55 psi) | ||||||||||||||||||
4 | Is any fuel pressure indicated? | -- | ||||||||||||||||||
Does the scan tool indicate an engine RPM? | -- | |||||||||||||||||||
Does the test lamp illuminate? | -- | |||||||||||||||||||
7 |
Does the test lamp illuminate? | -- | ||||||||||||||||||
Is the voltage near the specified value? | B+ | |||||||||||||||||||
9 | Connect the DMM between the 18X CKP sensor signal terminal and sensor ground terminal in the connector. Is the voltage within the specified range? | 6-8 V | ||||||||||||||||||
10 | Inspect for faulty terminal connections at the 18X CKP sensor. If a problem is found, repair as necessary. Refer to Wiring Repairs in Wiring Systems. Was a problem found? | -- | ||||||||||||||||||
11 | Connect the DMM between the 18X CKP sensor feed and engine ground. Is the voltage near the specified value? | B+ | ||||||||||||||||||
12 |
Was a problem found? | -- |
| |||||||||||||||||
13 |
Was a problem found? | -- | ||||||||||||||||||
14 |
Is the voltage near the specified value? | B+ | ||||||||||||||||||
15 | Locate and repair the short between the 18X CKP sensor signal CKT and the following CKTs:
Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | -- | |||||||||||||||||
16 |
Was a problem found? | -- | ||||||||||||||||||
17 |
Does the injector test lamp illuminate in any of the injectors? | -- | ||||||||||||||||||
18 |
Does the injector test lamp illuminate in any of the injectors? | -- | ||||||||||||||||||
19 |
Does the injector test lamp blink in each of the injectors? | -- | ||||||||||||||||||
20 | Did the injector test lamp blink for any of the injectors? | -- | ||||||||||||||||||
21 |
Was a problem found? | -- | ||||||||||||||||||
22 |
Does the test lamp illuminate? | -- | ||||||||||||||||||
23 | Locate and repair the open ignition positive feed circuit to the fuel injectors. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | -- | |||||||||||||||||
Is spark available at all cylinders? | -- | |||||||||||||||||||
25 | Is spark available at any cylinder? | -- | ||||||||||||||||||
26 |
Is the voltage within the specified range? | 6-8 V | ||||||||||||||||||
27 |
Was a problem found? | -- | ||||||||||||||||||
28 |
Was a problem found? | -- | ||||||||||||||||||
29 |
Was a problem found? | -- | ||||||||||||||||||
30 |
Was a problem found? | -- | ||||||||||||||||||
31 |
Was a problem found? | 5K-8K ohms | ||||||||||||||||||
32 |
Was a problem found? | 600 ohms/ ft | ||||||||||||||||||
33 |
Does the test lamp blink continuously while the engine is being cranked? | -- | ||||||||||||||||||
34 |
| -- | ||||||||||||||||||
Was a problem found? | -- | |||||||||||||||||||
36 |
Was a problem found? | -- | ||||||||||||||||||
37 | Repair an engine mechanical problem. Refer to Engine Noise Diagnosis in order to diagnose the following conditions:
Did you complete the repair? | -- | -- | |||||||||||||||||
38 | Test for faulty terminal connections at the ICM. If a problem is found, repair as necessary. Refer to Wiring Repairs in Wiring Systems. Was a problem found? | -- | ||||||||||||||||||
39 | Locate and repair the open in the ICM ground circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | -- | |||||||||||||||||
40 | Locate and repair the open in the ignition positive feed circuit to the ICM. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | -- | |||||||||||||||||
41 | Replace the 18X CKP sensor. Refer to Crankshaft Position Sensor Replacement . Did you complete the repair? | -- | -- | |||||||||||||||||
42 | Replace the ICM. Refer to Ignition Control Module Replacement . Did you complete the repair? | -- | -- | |||||||||||||||||
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 in Wiring Systems. Did you complete the repair? | -- | -- | |||||||||||||||||
44 | Test for faulty terminal connections at the PCM. If a problem is found, repair as necessary. Refer to Connector Repairs in Wiring Systems. Was a problem found? | -- | ||||||||||||||||||
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 repair? | -- | -- | |||||||||||||||||
Important: A replacement PCM must be reprogrammed. Refer to Powertrain Control Module Replacement/Programming . Replace the PCM. Did you complete the repair? | -- | -- |