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Discussion Starter · #1 ·
I am building a trike with a 2002 dodge grand caravan as the drive train. This was my daily driver for over 10 years. I cut away the body leaving the entire front intact. Removed dash leaving wiring intact. Motor ran fine until I started cutting out unwanted circuits. airbag squib lines replaced with 3.3-ohm resistors. Dash controls removed, overhead controls removed. Headlights work, motor cranks no start. I have an injector pulse but no ignition pulse. I do have voltage at the coil and injectors. No ignition pulse at any coil input equals no spark. I am fairly sure I remove some wires that need to be connected just not sure which. Any guidance or guess? Willing to try anything.
 

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Discussion Starter · #5 ·
Can you pull diagnostic codes out of the OBDII port?




ENGINE START-UP MODE

This is an OPEN LOOP mode. The following
actions occur when the starter motor is engaged.
If the PCM receives the camshaft position sensor
and crankshaft position sensor signals, it energizes
the ASD relay and fuel pump relay. These relays supply battery voltage to the fuel pump, fuel injectors,
ignition coil, and oxygen sensor heating element. If
the PCM does not receive the camshaft position sensor and crankshaft position sensor signals within
approximately one second, it de-energizes the ASD
relay and fuel pump relay.
The PCM energizes all injectors until it determines
crankshaft position from the camshaft position sensor and crankshaft position sensor signals. The PCM
determines crankshaft position within 1 engine revolution.
After determining crankshaft position, the PCM
begins energizing the injectors in sequence. The PCM
adjusts injector pulse width and controls injector synchronization by turning the individual ground paths
to the injectors On and Off.
Yes I can pull codes from the obd. Scan shows p1495 (normal with several vacuum lines open) p0352,p0353 (yep no spark signal) maybe should put a test lamp on the ASD output make sure it is staying active.
 

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Discussion Starter · #7 ·
I'd check the coils first with those codes. Do you know how to measure primary and secondary resistance on a coil?

Check the signal wire between the PCM and coils.

Check voltage drops- battery to coil, coil positive to negative, coil negative to chassis ground. Battery to PCM B positive, PCM B+ to negative, PCM Negative to ground.
Finally, voltage drop from coil negative to PCM Negative.


Fuel injected vehicles are extremely sensitive to ground path issues. You probably cut or removed a ground path. As good as you think everything on your project is grounded, I can guarantee that it is subpar compared to what an EFI computer actually wants, that's often the case.
I haven't checked for voltage drops yet. My first issues when cutting out the rear wiring was with grounds going to the seatbelts. Multiple grounds tied to body bolts were required to start. I did measure resistance between grounds today. The battery to the body is zero ohms. Various engine metal parts were from zero to 10 ohms. Planning on making some new grounding straps.
 

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Discussion Starter · #9 ·
Grounds are complicated, not simple like older cars. The ground distribution section of the service manual is like 30 schematics long.

There should be practically 0 ohms on any of them.

View attachment 61069




There are 11 major ground points-
View attachment 61070
I am interested in what PDF this is from. The page number and diagrams do not match the one I have. I believe mine is for 2004, not 100% sure. I have found several places where wire colors do not match.
 

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Discussion Starter · #10 ·
I am interested in what PDF this is from. The page number and diagrams do not match the one I have. I believe mine is for 2004, not 100% sure. I have found several places where wire colors do not match.
Doing a quick search I was able to match your pages to another manual. I was able to download a copy. May or may not make a difference but darn glad you posted this diagram.
 

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Discussion Starter · #12 ·
How well I know about the engine electronics changes. This motor is actually an 2006. Had to do major sensor swapping and timing hardware changes. After over 10 years and being the second owner I trust this drivetrain. I got the van from a close friend who bought it new.
 

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Discussion Starter · #15 ·
You are correct on the parts swapping for the 2006 motor to the 2002 van. Also had to swap the intake and fuel system. I do have some pics and videos of the project. Covid and having to try keeping a restaurant running ate all my time in 2020. I will have to figure how to post the pics here.
 

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Discussion Starter · #18 ·
Yup, 2004 diagram will not work. 2001-2003 were the same, and very similar to 1998-2000 3rd gen wiring.

To get a newer engine like the 2006 to work in the 2002, you would have needed to swap the timing gears/chain/cover and sensor, and the flex plate. Then swap the 2002 engine wiring harness to the 2006 engine.

Possibly a problem with the body wiring/bus? I've read of these vans not starting because of a broken power sliding door wire harness before. Now that you have the proper year wiring diagrams, you'll have much better chances at finding the problem.
Funny you mention the sliding door harness. The ground wiring for the sliding doors is exactly the straps that are behind the seats. No ground here equals no start. I believe I am hunting an ASD issue. I know the fuse and the relays are good and in the run position, I have power to the coil pack and to the injectors. In the start position, this power is off. I plan on checking the start/run outputs on the relay and the airbag module today.
 

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Discussion Starter · #20 ·
I believe that the ASD relay powers the fuel pump relay.
Did a fair bit of testing this evening. ASD relay work ok, swapped in another just to test. When turning the key on the ASD relay engages sending power to pin 30. This powers the fuel pump injectors and coil. The problem, it disengages pin 30 within 1 second. The fuel pump follows the same procedure. The signal to engage and disengage the ASD relay comes from the PCM. What issues prompt the ASD relay to shut down the engine?
 

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Discussion Starter · #22 ·
Post #3 on this page-




You are either not getting a valid crankshaft position sensor signal or camshaft position sensor signal, and the PCM is de-energizing the ASD relay.
Nothing in the area of the crankshaft sensor or the camshaft sensors have been removed or damaged. The motor ran fine until I started removing under dash wiring. The firewall and the abs have been removed. The ASD is turning off before cranking. I did have the issue you are covering when replacing the engine around 10 years ago.
 

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Discussion Starter · #24 ·
Exactly my thoughts on a ground path. I have been chasing and marking wires for weeks. It all worked until I cut the firewall out. I had the rear ground splices bolted to the airbag module bolts on the floor. I am really wondering if the airbag module is sending a bad signal to the pcm. If my thoughts are correct the airbag pic bus is one of the main items that cause the asd to trigger. Btw during today's tests I still have no action on the dash lights or gauges. I am almost ready to harvest a new/used interior wire harness. Or rebuild the cut one. I don't think the missing seatbelt lines would cause this.
 

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Discussion Starter · #26 ·
When I removed the airbag module the first time I had the crank but no start issue. Re-mounting the module had the motor running again. With this happening I assumed it had to be there for normal operation. I hope you can confirm this part is not needed.
 

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Discussion Starter · #29 ·
Powertrain should function without other systems attached. Don't have a van of that generation at the shop to test it on, but I've dealt with wrecked cars that needed lights off to be able to pass a rebuild inspection. Never seen an airbag keep any from cranking. Are you certain it was the airbag module you disconnected?
It cranks with no problems. It does not start. Further testing and voltage checks today. Didn't have much time to spend. I have 12 volts to the coil and injectors while cranking. Nothing to the hot wires with the key just on. I do have an injector pulse while cranking. I do not have ignition pulse while cranking. Also, chasing issues with the instrument panel and dash lights. I have power to the gauges but no lights or movement of the needles. I am attempting to add details as I go. Headlamps work turn signals do not. On a side note, I did have all the wires to the steering column off and the column removed for a while. I don't know if this could have caused any issues with the security key or not. Excuse me for being a bit flighty with my thoughts I am still having some after-effects from having the damn virus and being down for a few weeks. I am copying this reply to add it to the discussion with edy.
 

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Discussion Starter · #30 ·
I would suspect that the engine would automatically shut down in an accident, this is a simple and common safety feature, and this would be communicated by the airbag system.

But, the vehicle should immediately be able to restart for safety reasons. Not being able to start a vehicle and "drive" it immediately after a serious accident could be life threatening. Somebody could be pinned, the accident could be in a busy and dangerous area like the bottom of an icy hill...

I see this in industrial equipment. We put impact sensors that automatically lock out equipment. But anyone, even unauthorized users, are able to restart the equipment and drive it with limited function in emergency mode afterwards, even though they'd need RFID badge or password access to start it under normal situations.
It cranks with no problems. It does not start. Further testing and voltage checks today. Didn't have much time to spend. I have 12 volts to the coil and injectors while cranking. Nothing to the hot wires with the key just on. I do have an injector pulse while cranking. I do not have ignition pulse while cranking. Also, chasing issues with the instrument panel and dash lights. I have power to the gauges but no lights or movement of the needles. I am attempting to add details as I go. Headlamps work turn signals do not. On a side note, I did have all the wires to the steering column off and the column removed for a while. I don't know if this could have caused any issues with the security key or not. Excuse me for being a bit flighty with my thoughts I am still having some after-effects from having the damn virus and being down for a few weeks. I am copying this reply to add it to the discussion with edy.
 

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Discussion Starter · #33 ·
From the manual:
And power and ground distribution attached.
Thank you for the information. I haven't dug into manuals like this since the 70s while in the Army. On the turn signals, instrument cluster, and other items The key was in the run position. I do have power going thru the switch to the start and run lines. I do have a question about a term I haven't come to grips with yet. Wires that are labeled sense and return. Example "Ignition Switch Sense" "Ignition Switch Sense Return" I will be putting the files you sent to me asap.
BTW I love your tag line. If and when I get DT running I will have to work on a good tag line. DT being Dodge Trike ;)
 

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Discussion Starter · #36 ·
I was reading the manual for Megasquirt ECUs, might be needing one for the 4.0L swap I'm doing, and came across this information, what I was getting at with ground, but stated better.

View attachment 61085


View attachment 61086


View attachment 61087
Makes sense to me. When computers are involved the signal and the data being carried are much more than just connect/disconnect. I have started tracing reconnecting ground wires today. I have thought for a while now I have some ground issues. I pulled some of the grounding splices from the saved parts today. The connections show to be grounded but might not be activating the pcm correctly.
 

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Discussion Starter · #37 ·
Well guys I am still lost on this ignition pulse problem. Spent a good part of the day tracking down body wires that were removed. Checking voltages checking connections that kind of stuff. Tested the camshaft and crankshaft sensors 8 volt and 5 volts on both tests ok in the run position. Cranking the signal lines are active. Tested ignition coil and the resistance on primary and secondary are good. Measured resistance between grounds nothing more than 1 ohm. Measured voltages on the different B+. Nothing more than 0.1 volts. ASD relay. works as it should power the injector b+ fuel pump and ignition coil b+ for a second or so then shuts off. Turning the switch to start enables ASD relay sending b+ to all 3 again. Took both positive and negative battery terminals apart to clean the extra connectors to be sure of good b+ and grounds. My next step will be checking the ignition, b+, and ground lead's to the PCM. Also still no activity to the gauges dash lights or the turn signals. Posable I could have crossed something and cooked part of the PCM.
 

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Discussion Starter · #39 ·
Do you have a second battery to crank with? One battery wired to engine ground and starter B+, the other battery wired to the normal positive and negative battery cables. Leave the normal B+ cable from the harness disconnected from the starter.

This would power the van EFI system from one battery, and the starter independently on the second battery. It would eliminate any major noise issue from the starter.

Wondering if the instrument cluster has to be talking on the communication BUS for the 4th gen to run?
The instrument cluster does have a bus line going to it if that was what you were asking.
On the starter, I believe you are thinking about running the cranking from 1 battery and the electronics from the other battery. I am not sure where you are going with this suggestion.
 
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