Hi, I am new to the forums but I have read countless threads this week trying to solve my truck starting issue. You people here seem to have a wealth of knowledge so I thought I would take a chance and join. Any way here is my problem. My truck is a 1998 Dodge Ram 1500 Quad Cab 4x4 5.9 V8 with approx 101,000 miles. I have been having a rough idling issue for a few months. As soon as you start the truck hot or cold within about 15 min truck will almost want to stall. A few hard revs and she comes back to life. I have checked plugs, air fliter, gone through multiple tanks of gas ( for possible water in tank ), used cleaner to clean throttle body, and changed Idle Air Control Valve. I was about to clean the injectors bought cleaner and went to warm up my truck after driving it the day before with no problems. The truck would start but died immediately. I hear the fuel pump kick on. The odd thing was the none of the gauges would register. With the key in start I see the oil, temp and alternator gauge needles move to their base setting but not the gas gauge it doesn't move. When attempting to start the truck the Tach never moves even for the few seconds the truck is running. I have attempted the on off sequence with the key and get nothing. I did the trip check and get 900 920 921 940 950 and 999. If i just turn the key to start I see the dash lights come on off like its going through checks but the ABS and Airbag lights come back on as if there is a communication failure. I do not get the No Bus indication but my odometer does flash. All other accessories appear to work although I have not checked everything. I have checked all fuses and relays under the hood. I have reseated the PCM connectors and ohmed the four main grounds. At this point I am leaning towards a rebuilt PCM from ACE but any suggestions to save that money would be greatly appreciated. One last issue but I hope its not related is I know my ABS Module is bad pump stays running. The connector has been disconnected for about month while I was saving for the money to buy a rebuilt one from Module Masters. I think thats about it so again thanks for your help in advance...

 

Hello, let me offer some help.

There's a fair amount of information in your post. It's well described and, in outline form, it looks like this:

-We've had a truck that had a rough idle condition

-Attempted to resolve that by: cleaning the TB, replacing the IAC motor, checked the plugs.

-We've got a truck that starts and dies immediately as things progressively got worse.

-Noted fuel pump does kick in- audio noise as indicator

-We've got a no COMM error on the guages- (sounds like a possible ASD / FAILSAFE EVENT)

-No OBD codes are thrown.

-Odo FLASHING

-All relays verified good

-OHM test was performed on main grounds (4) points of temination

Ok, so, there's our outline which makes it much easier to digest and wrap out heads around.

Walking the path.

I am going to have to walk through this out loud in order to figure this one out.

The first failure mode was a 15 minute stall out. It's too bad it's not running now as I would have you verify fuel pressure. You reported a NO FUEL PUMP LEVEL (SENDING UNIT SIGNAL) which, can also be attributed to a spent pump ALTHOUGH- it also can be attributed to a NO POWER condition TO THE FUEL PUMP or, AUTOMATIC SHUT DOWN / failsafe mechanism. NO power IN, no voltage reference OUT to any of the EFI systems.

So, our first POSSIBLE failure mode is a spent / shorted fuel pump. Why: well, you reported a rough idle for a while and, after cleaning the TB, replacing the IAC motor etc, did not help and, over time, it worsened. A bad fuel pump will indeed induce a rough running and if the pressure is dropping as it heats up (which is normal due to expansion of the ID of the fuel delivery system components) the pressure dropped below the acceptable MIN value there's a good chance that the PCM initiated the failsafe mechanism command thus killing ALL power to all systems.

There's a strong chance that this is what's going on. The PCM may have shut the system down VIA the ASD relay. In the PDC (power distribution center / black box) located on the driver side, inner fender well, you will find a relay chart. It will depict where the ASD relay is.

ASD RELAY TEST: OHM and FUNCTIONAL TEST

Per Haynes manual, measure the coil resistance on primary and secondary to OEM spec.

The goal is to rule / factor out this component as the failure mechanism. If it passes OEM spec / test, we move onto the FUEL PUMP RELAY.

FUEL PUMP RELAY TEST:

-perform the same test as called out per OEM spec. Again, the goal is to factor out this component as a possible failure mechanism. If both components pass, we may be looking at a possible defective component or sensor that triggered the PCM shutdown event.

Next possible failure mode: Power Source

VOLTAGE supply is also suspect. If the ALT output is not reaching full output it will shut down. This will also progressively worsen over time due to loss of voltage.

-Check your battery without a load. Should be at 12.5 VDC

-Place the meter in the window facing you in the cockpit

-Check battery UNDER Load by placing the lights to ON

-Note reading

-Hit starter

-Note reading. If the voltage drops to <10 volts, and is slow to recover- there's a dead cell connector in the battery. R & R the battery.

Next Possible failure mode: FAULT in REGULATOR CKT

Bad voltage regulator CKT at the PCM thus, not meeting power requirements.


Next possible failure mode: Coil

If the coil goes south and stops putting out or, is partially open, shorted - it will induce a rough running condition as well. It will get worse as the coil shorts out more and more thus creating a larger voltage drop / loss at the secondary. However, it will trip an OBD code and, even with it disconnected, you would still be able to turn the vehicle over along with having power unless, it directly shorted to chassis ground thus sending 30-40 Kv into the system thus damaging the PCM.


Next possible failure mode: Fuel Pump

FUEL PUMP TEST:

Due to the fact that there is probability that the system is running a KILL command, you will NOT be able to test the fuel pump. If the vehicle is NOT running or, not able to run AT ALL, you have no way to verify FUEL PRESSURE. In this case, I would ask this question: How long has this fuel pump been installed. How many miles on this fuel pump etc. If it's been a really long time, chances are, you've either got one or two things going on and they are as follows:

1. Clogged filter at the pump. NOTE: the filter is located INSIDE the fuel tank and, in order to check / verify this, the fuel tank must be dropped, the pump is to be removed and checked. This can also be a possible failure mechanism.

2. The second possible failure mechanism is a failed pump motor that is locking up. The current draw is going to exceed the safety rating thus causing the failsafe mechanism at the PCM to shut down all power.


Next possible failure mode: Electrical Sensors

Bad CKPS or CPS (Crank and / or CAM sensor

If one has been going out, it will induce the same exact symptoms- rough running, stalling and no power due to it too, will cause the failsafe mechanism to execute the kill command.

Next possible failure mode: PCM related

Now, jumping right to the PCM level: There is also a possibility of a bad ground FROM the PCM to chassis. Medium level of probability there. Don't see it too often but, from time to time, it does manifest itself. Also, when probing grounds with a meter, be sure to DISCONNECT all harnesses at the PCM before OHM testing to prevent BLOWING voltage sensitive components.



Hope that helps,

CM

 

First off let me say thanks for responding. Now let me try to give you some answers to your suggestions...

I am going to have to walk through this out loud in order to figure this one out.

The first failure mode was a 15 minute stall out. It's too bad it's not running now as I would have you verify fuel pressure. You reported a NO FUEL PUMP LEVEL (SENDING UNIT SIGNAL) which, can also be attributed to a spent pump ALTHOUGH- it also can be attributed to a NO POWER condition TO THE FUEL PUMP or, AUTOMATIC SHUT DOWN / failsafe mechanism. NO power IN, no voltage reference OUT to any of the EFI systems.

Slight misunderstanding the truck would sputter and seem as if it was going to stall but would not actually stall. This would happen give or take within 15 min of either a cold or warm start. A few hard revs would clear this up and truck would drive normal from then on until shut off...

ASD RELAY TEST: OHM and FUNCTIONAL TEST

Per Haynes manual, measure the coil resistance on primary and secondary to OEM spec.

The goal is to rule / factor out this component as the failure mechanism. If it passes OEM spec / test, we move onto the FUEL PUMP RELAY.

FUEL PUMP RELAY TEST:

-perform the same test as called out per OEM spec. Again, the goal is to factor out this component as a possible failure mechanism. If both components pass, we may be looking at a possible defective component or sensor that triggered the PCM shutdown event

I had already performed functional tests of both the ASD and Fuel Pump relays by swapping them into the horn position since they were all the exact same part number. However if you think an ohm test of the coils will reveal something different I will do that as well...

Next possible failure mode: Power Source

VOLTAGE supply is also suspect. If the ALT output is not reaching full output it will shut down. This will also progressively worsen over time due to loss of voltage.

-Check your battery without a load. Should be at 12.5 VDC

-Place the meter in the window facing you in the cockpit

-Check battery UNDER Load by placing the lights to ON

-Note reading

-Hit starter

-Note reading. If the voltage drops to <10 volts, and is slow to recover- there's a dead cell connector in the battery. R & R the battery.

The battery itself is probably less than 6 months old and I have already done a no load test it read 12.5 Vdc. I will check the voltage under load in the morning...

The problem that concerned me was the way my gauges were acting. The fact that with the key in the start position my gas gauge did not operate. Plus none of the guages registered anything even when the engine ran for a few seconds before dying. No RPMs at all on the tach, no oil pressure, no volts nothing. Didn't think something like the fuel pump or coil would cause a condition like that. But as soon as I can I will go through your list and update you on the results... thanks again

 

Ok, now we have more information to factor in. The picture is becoming clearer.

Now we've got it runs fine up until 15 minutes after cold or warm as noted here: So, I know that after 3 minutes, the PCM goes into closed loop mode or, at least, it's supposed to. So, we know that after 15 minutes of running, it's supposed to be in closed loop mode, running off all sensor inputs and control systems are fully active.

The thing that is throwing me is that we may have TWO failures here and not just one. That's why this case is going to be more difficult to narrow down to a particular system.

Sputtering after warm or cold can be quite a few things:

-bad IAC motor or, loss of motor control due to fault at driver CKT at PCM
-clogged or partially restricted CAT
-partially clogged fuel pump inlet
-partially shorted fuel pump motor
-bad coil driver CKT at the PCM
-bad coil
-fault in the CKPS / CPS system
-clogged fuel injector baskets
-low power source

We are looking at a lot of possibilities and, none of those would kill the cluster other than the CKPS / CPS and low power source.

Let me ask you this: did you verify the voltage output of the charging system?

When testing, the swap is a quick and dirty test that may not really tell you what is going on. That only works if the component is dead. I always test 100% to rule it out.

-Always check the resistance of the coil on the relay along with performing a functional test. This involves applying power to the relay and then measuring. This is a functional test while, measuring with no voltage is a NON-operational test.

-In addition to that, I would also test the voltage coming INTO the ASD relay and note it. It is possible that the ASD and FUEL PUMP relays are fine however, the voltage that FEEDS them both IS NOT. Again, rule it all out and move on.


But, we have a major concern and that is: No instrument cluster when running. In order to determine where the fault is, I would have to trace it back through the schematics and find the systems affecting / associated with the cluster. If memory serves me correct, the COMM link is where this occurs. I recall posting about this months ago. The COMM / BUS is tied into the PCM.

The question is: at current, does the truck start: Y or N?

<IF> Yes: does it run for 15 minutes and sputter? Is the entire cluster dead or not? This is not yet clear to me. I want to know, when you get in, and you turn the key to <ON> is the cluster dead or not? Here, it reads: This means that they are not dead as indicated by the movement to the base setting so, we know the cluster is getting power.

Here, it reads totally opposite: I read that as there's nothing there- no action, nada, dead. So, if you could clarify if there's movement (power) at the time the key is turned to <ON>, that would tell me if there's power to the cluster or not.

Thanks,

CM

EDIT: Now, the other thing that just came to mind is: the ABS and other indicator. This is normally associated with a BUS failure such as when I forget to remove the scan tool and reflash tool from the data connector. I get those lamps that will come on indicating COMM failure.

 

Ok next couple of days are 12 hour workdays so I won't be able to do much diagnosis work but I will do my best to do a little everyday...


ASD RELAY TEST: OHM and FUNCTIONAL TEST

Per Haynes manual, measure the coil resistance on primary and secondary to OEM spec.

The goal is to rule / factor out this component as the failure mechanism. If it passes OEM spec / test, we move onto the FUEL PUMP RELAY.

FUEL PUMP RELAY TEST:

-perform the same test as called out per OEM spec. Again, the goal is to factor out this component as a possible failure mechanism. If both components pass, we may be looking at a possible defective component or sensor that triggered the PCM shutdown event.

Ohmed all relays of same part number not just ASD and Fuel all tested exactly the same. (Approximately 10) I believe the pin configuration was as follows:
Pins: 1 & 2 - 75 to 76.2 Ohms
Pins: 3 & 4 - Continuity
**No continuity between any other pins


Next possible failure mode: Power Source

VOLTAGE supply is also suspect. If the ALT output is not reaching full output it will shut down. This will also progressively worsen over time due to loss of voltage.

-Check your battery without a load. Should be at 12.5 VDC

-Place the meter in the window facing you in the cockpit

-Check battery UNDER Load by placing the lights to ON

-Note reading

12.5 VDC No load
12.2 VDC Under load ( multiple accessories on )


The question is: at current, does the truck start: Y or N?

Start, well that answer is subjective LOL. In my opinion it does start for seconds and then dies immediately. Nothing I do ie. giving it gas or anything keeps it running any longer than a few seconds...


<IF> Yes: does it run for 15 minutes and sputter? Is the entire cluster dead or not? This is not yet clear to me. I want to know, when you get in, and you turn the key to <ON> is the cluster dead or not? Here, it reads:

Quote:With the key in start I see the oil, temp and alternator gauge needles move to their base setting but not the gas gauge it doesn't move
With the key in start I see the oil, temp and alternator gauge needles move to their base setting but not the gas gauge it doesn't move
This means that they are not dead as indicated by the movement to the base setting so, we know the cluster is getting power.

Oil, Temp and alternator move to their base settings therefore powered but no input. Tach and Fuel gauge do nothing appear to have no power or input.


EDIT: Now, the other thing that just came to mind is: the ABS and other indicator. This is normally associated with a BUS failure such as when I forget to remove the scan tool and reflash tool from the data connector. I get those lamps that will come on indicating COMM failure.

I agree with some sort communications failure. ABS and Airbags do a system check and then go off well normally. Mine however are both staying on now. But you have to remember my ABS Module is bad so even before this the ABS light would go off then on but then the brake light would also come on and stay on. I know the Module is indeed bad but now the Airbag light comes on as well and the odometer flashes...

 

could it be as simple as the connector for the ABS shorting to ground? You said it was disconnected.

 

Been looking for the simple but no luck as of yet. The ABS connector is taped off. Plus I have been checking and reseating connectors through out the truck that appear to be any way connected according to the schematics I have... Thanks for the suggestion though.

 

This is a more difficult case and, looking back in history on here, I recall a similar incident that we went through line by line until we found the root cause to be rooted at the PCM level. A new one was put in and, boom, fired right up.

Ok, I'm now thinking back on that old post and, I believe that during questioning, I found a clue. I'm now going to ask you this same question that I had asked the other fella.

The question is, during any time of working on your truck, did you encounter an arc or spark when connecting the negative battery cable to the battery?

I think I may have mentioned this but, maybe not so, that being said, the reason I am asking is this:

When connecting the battery under loading conditions, it will draw current and arc / spark thus creating an IN-RUSH current condition which can KILL the PCM. This is why in some posts, I mention to make sure that all the doors are closed (DOME LIGHT CKT), the lights are off, etc etc, because of this problem. Some get lucky and have never had that happen. I had it happen ONCE- while on the road. I needed to clear the PCM for some reason and, I left my stereo on, the door open and, a directional on. I was in a rush, a bit nervous, tired and failed to pay attention to what I was doing.

I connected the negative terminal and it arced. I went to start it and, all the lights went dim- nothing. Blew the damn PCM. Live and learn at the school of hard knocks. All my gauges went dead, it wouldn't start for nothing- deader than a doornail.

Just a thought as, I recall, in that old thread, we went on for a long time and, before we keep on with this, that and everything else, there may have been some information that we forget to factor into our troubleshooting plan.

CM

 

This is a more difficult case and, looking back in history on here, I recall a similar incident that we went through line by line until we found the root cause to be rooted at the PCM level. A new one was put in and, boom, fired right up.

Ok, I'm now thinking back on that old post and, I believe that during questioning, I found a clue. I'm now going to ask you this same question that I had asked the other fella.

The question is, during any time of working on your truck, did you encounter an arc or spark when connecting the negative battery cable to the battery?


I myself have been leaning towards the PCM from the beginning but was hoping for a cheaper fix however to answer your question the battery cable had not been disconnected. The battery had been installed give or take last winter and all the problems have been presenting themselves within the past month or so meaning the idling issue. The non starting problem happened a few days ago. Truck was shutoff the night before without an issue and just wouldn't start in the morning...

 

If I didn't have to finish rewiring a Hot Rod today, I would be online to help you to at least check the fuel delivery system.

I have a growing suspicion on this case BASED on previous information- rough idle that is leading me to believe that it may not be PCM related but rather being in auto shutdown mode.

What I would like to know is whether an automatic shutdown event has occurred and, to test that, here's what I want you to do.


TEST 1:

I want you to remove power by disconnecting the negative terminal on the battery for 30 seconds to one minute.

Making sure all CKTS are <OFF>, reconnect the battery.

Get in the truck and turn to <KEY ON> DO NOT START IT at this time.

Note gauge activity. Power and movement and any anomalies. (flashing ODO etc)

<START> the vehicle. (Try to anyways)

Does it start? Y / N? Not turn over but, actually start up.

Does it run for x- minutes Y / N?

Does it run for 3-seconds and shut down? Y / N

Do you have any input at the gauges during this time Y / N?

TEST 2:

Now, again, disconnect the battery and wait.

Reconnect and, this time, turn the key to <START / RUN>

Does it run for X-minutes Y / N?

Does it run for 3 seconds Y / N?

The answers to those questions will provide some good information as to whether or not she's going into auto shutdown mode or not.

I would have explained out why we are doing this but, I just don't have time. I've got to run. Try that and report back and, during the day, I'll pop online to see the results.

CM