Jeep Grand Cherokee Crank, No Start

11 May 2015 | Author: | Comments Off on Jeep Grand Cherokee Crank, No Start

I have an ODB code reader and it no fault codes. I changed the pump relay and the ASD (Auto Down) relay. I also the fuel pump pressure it was running and it was steady at about 31 with no vacuum it rose to 40 as per the

I also tested the fuel regulator with no issues

The dealer I bought it off wants to the fuel pump but I do no think it is the this is an electrical issue. I ran a Carfax on this and it had a note at miles that fuel replaced/repaired. So I think this was being chased for a while.

I also noticed that the lights when the key is first on are not working in the right sequence.

I am the impression that I was supposed to see the Engine light for three then the bells and other go out. Sometimes when It not start I do not see the check engine come on. I am thinking of a few problems, but I am not

Crank Position sensor? I tell if this is looked at by the PCM in open loop mode.

CAM sensor? I cannot tell if is looked at by the PCM when in open mode.

Heated O2 sensor. is NOT supposed to be looked at when in loop mode, but its design has a in it and it could explain the jittering of the But I think this is a long

Ignition Key switch is very and wobbly. I am wondering if this has to do with it? I checked the ignition with the Key ON and OFF and the ODB diagnostic tool a change in state from low to when the key was on and off respectively

I have noticed flakiness in the security system, door only work in one direction (unlock), then other they work bi-directionally.

And a faulty PCM.

Any help be greatly appreciated!




A. There are nine modes of for this engine management But in this case we only to concern ourselves with the two. And they are:

Switch On:

This is an OPEN mode. When the SFI system is by the ignition switch, the following occur:

The PCM prepositions the idle air (IAC) motor.

The PCM reads air pressure from the manifold pressure (MAP) sensor and the basic fuel strategy.

The PCM the throttle position sensor and engine coolant temperature sensor input. The PCM uses inputs to modify fuel

Intake air temperature (IAT) is monitored.

ASD relay is energized for 3

Fuel pump is energized for 1 unless engine is running or

Oxygen sensor heating is energized.

Engine Start-Up:

is an OPEN LOOP mode. the starter motor is engaged, the PCM input from:


Crankshaft position (CKP)

Engine coolant temperature sensor

Intake air temperature (IAT)

Throttle position sensor

Camshaft position (CMP)

Starter relay

Based on inputs the PCM will:

Monitor position sensor. If no signal is within 3 seconds, the PCM will down the fuel injection

Supply the injectors with a path, firing all injectors the PCM determines crankshaft position.

proper ignition timing.

we need to determine if there is a or ignition problem. Pull a line off the intake manifold and some carburetor cleaner it and try to start it. If it starts and runs as as the carburetor cleaner lasts, we we have a fuel problem.

If we have an ignition problem.

If it is an problem it could be due to a bad Crankshaft Sensor (CKP), Camshaft Sensor (CMP) or a bad Ignition

To do a complete test of the CKP circuit, need a scan tool. But you can do a test of the CKP with an ohmmeter.

the rear of the right cylinder disconnect CPS wiring harness from main wiring

Place an ohmmeter across B and C of the CPS connector. The meter reading be open (infinite resistance). sensor if resistance is indicated.

For this test, an analog voltmeter is needed. Do not remove the connector from the distributor. To a complete test of the Camshaft Sensor and its circuitry, refer to the DRB II tester.

Also see the appropriate Diagnostic To test the sensor only, to the following:

Using small clips, insert them the backside of the distributor wire connector to make contact the terminals. Be sure that the is not damaged when inserting the clips. Attach voltmeter to these paper clips.

the positive ( + ) voltmeter lead the sensor output wire. is done at the distributor wire connector.

Jeep Grand Cherokee

Connect the negative ( ) voltmeter lead into the wire.

Set the voltmeter to the 15 Volt DC

Remove distributor cap from (two screws). Rotate the engine until the distributor is pointed towards the rear of The movable pulse ring now be within the sensor pickup.

ignition key to ON position. Voltmeter read approximately 5.0 volts.

If is not present, check the voltmeter for a good connection.

If voltage is not present, check for voltage at the wire.

If voltage is not present at wire, check for voltage at pin 7 of Control Module (PCM) 60 pin Leave the PCM connector connected for test.

If voltage is still not perform vehicle test the DRB II diagnostic scan tool.

If voltage is present at pin 7, but not at the supply

Check continuity between the wire. This is checked the distributor connector and pin 7 at the PCM. If is not present, repair the harness as

Check for continuity between the Position Sensor output and pin 44 at the PCM. If continuity is not present, the harness as necessary.

Check for between the ground circuit at the distributor connector and ground. If is not present, repair the harness as

While observing the voltmeter, the engine with ignition The voltmeter needle should between 0 and 5 volts while the is cranking. This verifies the camshaft position sensor in the is operating properly and a sync signal is being generated.

If pulse signal is not present, of the Camshaft Position Sensor is

When an unauthorized entry the vehicle occurs, the VTSS a message via the CCD bus to the Powertrain Control (PCM) that it is not OK to start the The PCM then zeroes out the pulse to the fuel injectors after the has been started, thus down the engine (start and condition). The engine will not until the system is disarmed.

If is what’s happening, a noid plugged into one of the injector will not flash.

Added 3/25/2004

Hi Vince: I wanted to let you know on the Jeep fixed the issue.

After I got mail I found a break in the door wiring harness. I that the door locks not working and when I pulled on the to door jam harness, the door would once again working.

I suspect that the system, as you mention in your was also intermittently getting a from the door locks were malfunctioning and in turn was a no start signal to the ECM. If I correctly, the door alarms on year are pretty simple and to work in conjunction with the

So In the end the dealer that I bought the car changed the ECM, then the wiring harness and all is fine Although I bet the door wiring would have done the by itself. But it cost me $0.00 so I complain that I have a new ECM in a 10 old car.

Thanks again for the

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Vincent T. Ciulla

Jeep Grand Cherokee
Jeep Grand Cherokee
Jeep Grand Cherokee
Jeep Grand Cherokee
Jeep Grand Cherokee
Jeep Grand Cherokee

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