Circuit Description
This engine is equipped with a distributorless ignition system called the electronic ignition (EI) system. The primary circuit of the EI system consists of 2 separate ignition coils, an electronic ignition control module (ICM) and a crankshaft position (CKP) sensor as well as the related connecting wires and the ignition control (IC) portion of the Powertrain Control Module (PCM). Each secondary circuit consists of the secondary winding of the coil, spark plug wires, and the spark plugs.
Important: The camshaft position (CMP) sensor is only used for a misfire detection and is not part of the ignition system.
Diagnostic Aids
Check for the following conditions:
| • | The Throttle Position (TP) sensor binding or sticking in wide open throttle position. |
| • | The Throttle Position (TP) sensor for a shorted or open circuit. |
| • | Water or foreign material in the fuel. |
| • | Low compression (timing chain failure). |
Test Description
The numbers below refer to the step numbers on the Diagnostic Table.
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The Powertrain OBD System Check prompts the technician to complete some basic checks and store the freeze frame and failure records data on the scan tool if applicable. This creates an electronic copy of the data taken when the malfunction occurred. The information is then stored in the scan tool for later reference.
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Diagnosis of the DTCs that may be set could lead to the cause of the Cranks But Will Not Run condition.
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The PCM grounds will only cause a problem if all the grounds are not making a good connection. If a PCM ground problem is suspected, the most probable place to check is where all the grounds meet at the engine block.
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Locate and repair any shorts that may have caused the fuse to open before replacing the fuse.
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A TP sensor that reads too high may cause an incorrect fueling condition.
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An engine that has not been started should display ECT and IAT temperatures that are relatively close to each other. During the warmer weather, the IAT readings maybe slightly higher than the ECT readings.
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If the scan tool loses serial data only while cranking the engine, then the ignition switch is not sending voltage to the PCM while in the crank position.
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This step looks for a normal barometer reading and a change in MAP sensor values while cranking the engine. This step verifies the MAP sensor can detect the change in the manifold pressure that occurs while cranking the engine. Compare any questionable barometer readings with readings from another vehicle.
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While cranking the engine, the CKP Activity (7X reference) should increment to 255, then rollover to 0.
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By testing for spark on all 4 plug wire leads using a spark tester , each ignition coils ability to produced at least 25,000 volts is verified.
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The CKP sensor should output a voltage near 1100-1300 mV as the crankshaft turns. It is possible to trigger the ICM with a voltage as low as 200 mV. If no voltage is produced, a poor CKP sensor electrical connection or malfunctioning CKP sensor is indicated.
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The test light connected to B+ simulates a reference signal to the PCM. An fuel injector test light can be installed and will blink for every other touch of the test light if the CKP Activity (7X reference) circuit, the PCM and the fuel injector driver are all functioning properly.
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The replacement PCM must be programmed and the crankshaft position system variation procedure must be performed. Refer to the latest Techline procedures for PCM programming.
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The fuel pump is turned ON by the PCM for 2-3 seconds after the ignition is first turned ON. This step checks to see if the fuel pump and fuel pump relay are operating correctly and if the fuel pressure is within the proper range. Refer to the Fuel System Diagnosis for the fuel pressure gage installation procedure.
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Battery voltage should be available at the fuel injector ignition positive voltage circuit whenever the fuel pump power supply circuit is switched ON and when the PCM is receiving ignition pulses, during engine cranking or when the engine is running. The ignition must be turned OFF for at least 10 seconds to assure that the PCM powers down and will then switch the fuel pump back ON for 2-3 seconds when the ignition is turned back ON.
Step | Action | Value(s) | Yes | No | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | |||||||||
Are DTCs P0601, P0602, P1621, P1626, P1631, or P1632 set? | -- | Go to the applicable DTC tables | ||||||||
Inspect the PCM ground connection at the engine block. Is the ground connection OK? | -- | |||||||||
4 | Inspect the F/P-INJ, or IGN fuses. Are the fuses OK? | -- | ||||||||
5 |
Was it necessary to add fuel? | -- | ||||||||
Is the action complete? | -- | |||||||||
Does the TP sensor read less than the specified value? | 1.0V | Go to DTC P0123 Throttle Position (TP) Sensor Circuit High Voltage | ||||||||
With the scan tool installed. Is the Engine Coolant Temperature (ECT) relatively close to the Intake Air Temperature (IAT)? | -- | Go to DTC P0118 Engine Coolant Temperature (ECT) Sensor Circuit High Voltage | ||||||||
Crank the engine while watching the MAP sensor readings. Was serial data lost while cranking the engine? | 4.0V | |||||||||
Does the MAP sensor read over the specified value and then change while cranking the engine? | 4.0V | |||||||||
Check to see if the CKP activity counter increments while cranking the engine with the scan tool. Does the CKP activity counter increment while cranking the engine? | -- | |||||||||
12 | Repair voltage loss to the PCM from the ignition switch. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | -- | |||||||
13 |
Does the test light illuminate? | -- | ||||||||
14 |
Was a repair necessary? | -- | ||||||||
15 |
Was a repair necessary? | -- | ||||||||
Is spark observed on all of the wires? | -- | |||||||||
17 |
Is the resistance reading within the specified value? | 700-1,300ohms | ||||||||
18 |
Is the CKP sensor within the specified value? | 700-1,300ohms | ||||||||
Is the voltage reading more than the specified value? | 200 mV | |||||||||
20 |
Was a repair necessary? | -- | ||||||||
21 |
Was a repair necessary? | -- | ||||||||
Does the CKP activity counter increment as the test lamp touches B+? | -- | |||||||||
23 | Repair the open or a short in the CKP sensor electrical harness. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | -- | |||||||
24 | Replace the CKP sensor. Refer to Crankshaft Position Sensor Replacement . Is the action complete? | -- | -- | |||||||
25 |
Was repair necessary? | -- | ||||||||
26 | Repair the circuit as necessary. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | -- | |||||||
27 |
Did the test lamp flash when the engine was cranking? | -- | ||||||||
28 |
Was a repair necessary? | -- | ||||||||
29 | Replace the ICM. Refer to Ignition Control Module Replacement . Does the engine start and continue to run? | -- | ||||||||
30 | Inspect the PCM for poor connections. Are the connections OK? | -- | ||||||||
31 | Repair the connector or connections. Refer to Wiring Repairs or Connector Repairs in Wiring Systems Is the action complete? | -- | -- | |||||||
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Important:: Program the replacement PCM. Refer to Powertrain Control Module Replacement/Programming . Replace the PCM. Is the action complete? | -- | -- | ||||||||
33 | Replace the malfunctioinng ignition coil. Refer to Ignition Control Module Replacement . Is the action complete? | -- | -- | |||||||
Install a fuel pressure gauge and note pressure after ignition is ON for 2 seconds. Is the fuel pressure within the specified value? | 284-325 kPa (41-47 psi) | |||||||||
Does the test lamp blink on all cylinders? | -- | |||||||||
36 |
Was spark plug replacement necessary? | -- | Go to Diagnostic Aids | |||||||
37 | Repair the open in the fuel pump and injector ignition positive voltage circuit. Refer to Fuel Pump Electrical Circuit Diagnosis . Is the action complete? | -- | -- | |||||||
38 |
Does the engine start and continue to run? | -- | ||||||||
39 |
Are any DTCs displayed? | -- | Go to the applicable DTC table | System OK |
