Engine Cranks But Does Not Run SFI
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 PCM. Each secondary circuit consists of the secondary winding of the coil, 2 connecting metal strips molded into the coil housing, the spark plug boot/connector assemblies 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) |
| • | A slow responding EGR Valve |
Test Description
Number(s) below refer to the step number(s) 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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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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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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Check for possible voltage loss to the PCM including the ignition switch itself.
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By installing the spark plug jumper leads and testing for spark on all 4 plug wire leads, each ignition coil(s) ability to produced at least 25,000 volts is verified.
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The CKP sensor core is a magnet, therefore it should be magnetized.
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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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Notice: Do not leave the jumper wire connected to the PCM IC circuit connector for longer than 5 seconds at a time. Failure to do so may damage the ignition coil and/or the Ignition Control Module.
This step checks the ignition control circuits and the ICM.
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The replacement PCM must be reprogrammed and the crankshaft position system variation procedure must be performed. Refer to the latest Techline procedures for PCM reprogramming and to the Powertrain Control Module (PCM) for the Crankshaft Position System Variation Procedure .
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Battery voltage should be available at the fuel injector ignition feed circuit whenever the fuel pump power feed circuit is switched ON and when the PCM is receiving ignition pulses, during engine cranking or when the engine is running. The ignition switch 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 switch is turned back ON.
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The fuel pump is turned ON by the PCM for 2-3 seconds after the ignition switch 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.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | |||
Are DTCs P0601, P0602, or P1621 set? | -- | Go to the applicable DTC tables | ||
Inspect the PCM ground connection at the engine block. Is the ground connection OK? | -- | |||
4 | Inspect the fuel pump and injector ignition feed fuse. Is the fuse OK? | -- | ||
5 | Repair PCM ground connection. Is the action complete? | -- | -- | |
6 | Check the fuel level and add fuel if necessary. 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 | ||
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 | ||
Does the MAP sensor read over the specified value and then change while cranking the engine? | 4.0V | |||
Crank the engine. Does the CKP Active Counter increment while cranking? | -- | |||
Was serial data lost while cranking the engine? | -- | |||
Repair voltage loss to the PCM from the ignition switch. Is the action complete? | -- | -- | ||
Is spark observed on all of the cables? | -- | |||
15 |
Is the resistance reading within the specified value? | 700-1300ohms | ||
Is the CKP sensor magnetic with undamaged terminals and the resistance with the specified value? | 700-1300ohms | |||
Is the voltage reading greater than the specified value? | 200 Mv | |||
Connect a test light to B+ and touch the cavity D of the ICM harness electrical connector and then the cavity F. Does the CKP Activity Counter increment as the test light touches cavity F? | -- | |||
19 | Repair the open or a short in the CKP sensor electrical harness. Is the action complete? | -- | -- | |
20 | Replace the CKP sensor. Is the action complete? | -- | -- | |
21 |
Does test light illuminate? | -- | ||
22 | Connect a test light to ground and probe cavity B on the 2 pin ICM electrical connector. Does test light illuminate? | -- | ||
23 | Repair the malfunctioning ground circuit. Is the action complete? | -- | -- | |
24 | Check the CKP Activity (7X Reference) circuit for open or a short and repair as necessary. Was repair necessary? | -- | ||
25 | Repair the malfunctioning ICM ignition feed circuit. Is the action complete? | -- | -- | |
Notice: Do not leave the jumper wire connected to the PCM IC circuit connector for longer than 5 seconds at a time. Failure to do so may damage the ignition coil and/or the Ignition Control Module. Does a spark jump across the spark tester? | -- | |||
27 | Using a DVM, measure the resistance of the spark plug cable that the spark plug tester did not spark. Is the resistance of the spark plug cable less than the specified value? | 30000ohms | ||
28 |
Is the secondary coil resistance within the specified value? | 5-8K ohms | ||
29 |
Was spark observed on the spark tester? | -- | ||
30 | Replace the ICM. Is the action complete? | -- | -- | |
31 | Inspect the PCM electrical connector and connections. Are the connections OK? | -- | ||
32 | Check the affected cylinders ignition control circuit for an open or short and repair as necessary. Was a repair necessary? | -- | ||
33 | Repair the connector or connections. Is the action complete? | -- | -- | |
Replace the PCM. Is the action complete? | -- | -- | ||
35 | Replace the spark plug cable. Is the action complete? | -- | -- | |
36 | Replace the malfunctioing ignition coil. Is the action complete? | -- | -- | |
Does the test light blink on all cylinders? | -- | |||
Install a fuel pressure gauge and note pressure after ignition is ON for 2 seconds. Is the fuel pressure between the specified values? | 284-325 kPa (41-47 psi) | |||
39 | Check for fouled spark plugs and replace if necessary. Was spark plug replacement necessary? | -- | Go to Diagnostic Aids | |
40 | Repair the open in the fuel pump and injector ignition feed circuit. Is the action complete? | -- | -- | |
41 |
Does the engine start and continue to run? | -- | ||
42 |
Are any DTCs displayed? | -- | Go to Applicable DTC Table | System OK |
Engine Cranks But Does Not Run Fuel Pump Circuit
Circuit Description
When the ignition is turned ON, the powertrain control module (PCM) turns ON the in-tank fuel pump. The pump will remain ON as long as the PCM is receiving ignition reference pulses from the electronic ignition control module (ICM). If there are no reference pulses, the PCM will shut OFF the fuel pump about 2-3 seconds after the ignition is turned ON, about 10 seconds after the reference pulses stop.
The fuel pump delivers fuel to the fuel rail and fuel injectors, then to the fuel pressure regulator, where the system pressure is controlled to 283-324 kPa (41-47 psi) with no manifold vacuum or 214-303 kPa (31-44 psi) at idle. Excess fuel is then returned to the fuel tank.
Improper Fuel System pressure will result in one or all of the following symptoms:
| • | Cranks But Will Not Run |
| • | DTC P0171 |
| • | DTC P0172 |
| • | DTC P1171 |
| • | DTC P0300 |
| • | Cuts out, may feel like an ignition problem |
| • | Poor fuel economy, loss of power |
| • | Hesitation |
Diagnostic Aids
An intermittent may be caused by a poor connection, rubbed through wire insulation or a wire broken inside the insulation. Check for a poor connection or damaged harness. Inspect the PCM harness and connectors for the following items:
| • | Improper mating |
| • | Broken locks |
| • | Improperly formed or damaged terminals |
| • | Poor terminal to wire connections |
| • | Damaged harnesses |
Test Description
Number(s) below refer to step number(s) on the Diagnostic Table.
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The Powertrain OBD System Check prompts the technician to complete some basic checks and stores 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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If the no start condition was due to a open fuse, locate and repair any shorts that may have caused the fuse to open before replacement.
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This step determines if the fuel pump circuit can be controlled by the PCM. The PCM should energize the fuel pump relay and turn the fuel pump ON when commanded by the scan tool. If the engine is not cranking or running, the PCM should de-energize the relay and turn OFF the fuel pump after 2-3 seconds.
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Jumpering CKT 120 to CKT 839 verifies that the fuel pump relay ignition feed circuit, the fuel pump feed circuit, the fuel pump and fuel ground are all OK.
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Check for an open CKT 451.
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Replacement PCMs must be reprogrammed and the crankshaft position system variation procedure must be performed. Refer to the latest Isuzu Technical Communication System (ITCS) information for programming procedures and also refer to the Powertrain Control Module (PCM) .
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This step checks CKT 150 on the body side of the body harness only. If CKT 150 is OK, then CKTs 120 or 150 in the fuel tank harness or the fuel pump itself is malfunctioning.
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This test will determine if a short to ground on CKT 120 caused the fuse to open. To prevent mis-diagnosis, be sure the fuel pump harness is disconnected before the test.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | Go to | ||
Inspect the fuel pump relay fuse. Is the fuse OK? | -- | |||
Does the in-tank fuel pump run when commanded ON? | -- | Go to Fuel System Diagnosis | ||
Does the fuel pump run? | -- | |||
5 |
Does the test light illuminate? | -- | ||
6 | With a test light connected to ground, probe the ignition feed terminal to the fuel pump relay. Is the test light ON? | -- | ||
With a test light connected to B+, probe the ground terminal to the fuel pump relay. Is the test light ON? | -- | |||
8 | Check for an open or short to ground in the fuel pump control circuit and repair as necessary. Was a repair necessary? | -- | ||
9 |
Does the test light illuminate? | -- | ||
10 | Repair the open in the ignition feed circuit for the fuel pump relay. Is the action complete? | -- | -- | |
11 | Replace the fuel pump relay. Is the action complete? | -- | -- | |
12 | Repair the open ground circuit to the fuel pump relay. Is the action complete? | -- | -- | |
13 | Inspect connections and terminals at the PCM and repair as necessary. Was a repair necessary? | -- | ||
14 | With a test light connected to B+, probe the fuel pump ground circuit (body side). Does the test light illuminate? | -- | ||
15 | Repair the open fuel pump feed circuit. Is the action complete? | -- | -- | |
Replace the PCM. Refer to Powertrain Control Module Replacement/Programming . Is the action complete? | -- | -- | ||
Check the fuel pump feed and ground circuits in the fuel pump harness for an open and repair as necessary. Was a repair necessary? | -- | |||
18 | Repair the open fuel pump ground circuit. Is the action complete? | -- | -- | |
19 | Replace the fuel pump. Is the action complete? | -- | -- | |
Does the test light illuminate? | -- | |||
21 | Repair the short to ground in the fuel pump feed circuit. Is the action complete? | -- | -- | |
22 | With the test light still connected to B+, probe the fuel pump relay ignition feed circuit terminal. Does the test light illuminate? | -- | ||
23 | Repair the short to ground in the fuel pump relay ignition feed circuit. Is the action complete? | -- | -- | |
24 | Check the fuel pump feed circuit in the fuel pump harness for a short to ground and repair as necessary. Was a repair necessary? | -- | ||
25 |
Does the engine start and continue to run? | -- | ||
26 |
Are any DTCs displayed that have not been diagnosed? | -- | Go to applicable DTC table | System OK |
