Refer to Engine Controls Schematics
Ignition System, Knock Sensors
.
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 to fire 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 broken wire inside the insulation. Check for the following items:
| • | Poor connection or damaged harness -- Inspect the PCM and ignition control module harnesses and connectors for the following conditions: |
| • | Improper mating |
| • | Broken locks |
| • | Improperly formed or damaged terminals |
| • | Poor terminal to wire connection |
| • | 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 . |
| • | Faulty or skewed TP sensor. With a scan tool, verify that the displayed value at closed throttle is 0 percent. |
Test Description
The numbers below refer to the step numbers on the diagnostic table:
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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.
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Ensures that the ICM has the proper voltage supply and ground.
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Verifies that the ICM is supplying the proper sensor feed voltage.
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Check 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.
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If the 18X and CKP Sync signals to the ICM or the 18X and 3X reference signals to the PCM short together the vehicle will not start and run. However, there will be spark and fuel injector pulses.
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This vehicle is equipped with a PCM which utilizes an Electrically Erasable Programmable Read Only Memory (EEPROM). When the PCM is being replaced, the new PCM must be programmed.
Step | Action | Values | Yes | No | ||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | ||||||||||||||||||
2 |
Important: If the engine cranks and does not run, test the ignition relay feed circuits to and from the ignition relay. Refer to Power Distribution Schematics and Circuit Testing in Wiring Systems. Important: Before proceeding with this diagnostic table, ensure that the vehicle battery is fully charged. Important: If any DTCs are stored as failed since code clear (except P1374, P0336, or P0341), diagnose the DTCs before continuing with this table. Refer to Diagnostic Trouble Code (DTC) List/Type
Did you find and correct any conditions? | -- | ||||||||||||||||||
3 | With a scan tool, command the fuel pump ON. Does the fuel pump turn ON? | |||||||||||||||||||
4 |
Is the fuel pressure within the specified values and holding? | 333-376 kPa (48-55 psi) | ||||||||||||||||||
Does the scan tool indicate an engine RPM? | -- | |||||||||||||||||||
Does the test lamp illuminate? | -- | |||||||||||||||||||
7 |
Does the test lamp illuminate? | -- | ||||||||||||||||||
Does the voltage measure near the specified value? | B+ | |||||||||||||||||||
9 | Connect a DMM between the 18X CKP sensor signal circuit and sensor ground circuit at the connector. Does the voltage measure near the specified value? | 6-8 V | ||||||||||||||||||
10 | Inspect for poor terminal connections at the 18X CKP sensor. If a problem is found, repair as necessary. Refer to Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | ||||||||||||||||||
11 | Connect a DMM between the 18X CKP sensor feed circuit and engine ground. Does the voltage measure near the specified value? | B+ | ||||||||||||||||||
12 |
Did you find and correct the condition? | -- |
| |||||||||||||||||
13 |
Did you find and correct the condition? | -- | ||||||||||||||||||
14 |
Does the voltage measure near the specified value? | B+ | ||||||||||||||||||
15 | Locate and repair the short between the 18X CKP sensor signal circuit and the following circuits:
Refer to Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | -- | |||||||||||||||||
16 |
Did you find and correct the condition? | -- | ||||||||||||||||||
17 |
Does the injector test lamp illuminate for any of the injectors? | -- | ||||||||||||||||||
18 |
Does the test lamp illuminate for any of the injectors? | -- | ||||||||||||||||||
19 |
Did the injector test lamp blink for each injector? | -- | ||||||||||||||||||
20 | Did the injector test lamp blink for any of the injectors? | -- | ||||||||||||||||||
21 |
Did you find and correct the condition? | -- | ||||||||||||||||||
22 |
Does the test lamp illuminate for each injector? | -- | ||||||||||||||||||
23 | Locate and repair the open ignition positive feed circuit to the fuel injectors. Refer to Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | -- | |||||||||||||||||
Is spark available at all cylinders? | -- | |||||||||||||||||||
25 | Is spark available at any cylinder? | -- | ||||||||||||||||||
26 |
Does the voltage measure near the specified value? | 6-8 V | ||||||||||||||||||
27 |
Did you find and correct the condition? | -- | ||||||||||||||||||
28 |
Did you find and correct the condition? | -- | ||||||||||||||||||
29 |
Did you find and correct the condition? | -- | ||||||||||||||||||
30 |
Did you find and correct the condition? | -- | ||||||||||||||||||
31 |
Did you find and correct the condition? | 5K-8K ohms (5000-8000 ohms) | ||||||||||||||||||
32 |
Did you find and correct the condition? | 600 ohms /ft | ||||||||||||||||||
33 |
Does the test lamp blink continuously while the engine is being cranked? | -- | ||||||||||||||||||
34 |
Did the spark plug inspection reveal excessive fouling? | -- | Go to Oil Consumption Diagnosis . | |||||||||||||||||
Did you find and correct the condition? | -- | |||||||||||||||||||
36 |
Did you find and correct the condition? | -- | ||||||||||||||||||
37 | Repair the engine mechanical problem. Refer to Engine Compression Test in Engine Mechanical to diagnose the following conditions:
Did you complete the repairs? | -- | -- | |||||||||||||||||
38 | Inspect for poor terminal connections at the ICM. If a problem is found, repair as necessary. Refer to Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | ||||||||||||||||||
39 | Locate and repair the open in the ICM ground circuit. Refer to Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | -- | |||||||||||||||||
40 | Locate and repair the open in the ignition positive feed circuit to the ICM. Refer to Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | -- | |||||||||||||||||
41 | Replace the 18X CKP sensor. Refer to Crankshaft Position Sensor Replacement . Did you complete the replacement? | -- | -- | |||||||||||||||||
42 | Replace the ICM. Refer to Ignition Control Module Replacement . Did you complete the replacement? | -- | -- | |||||||||||||||||
43 | Locate and repair the short to ground in the fuel injector control circuits associated with the injector test lamps that stayed ON. Refer to Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | -- | |||||||||||||||||
44 | Inspect for poor terminal connections at the PCM. If a problem is found, repair as necessary. Refer to Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | ||||||||||||||||||
45 | Replace the ignition coils associated with the cylinders that did not have spark. Refer to Ignition Coil Replacement . Did you complete the replacement? | -- | -- | |||||||||||||||||
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Important: Replacement PCM must be programmed. Replace the PCM. Refer to Powertrain Control Module Replacement/Programming . Did you complete the replacement? | -- | -- |
