[SOLVED] The strangest problem I have ever encountered on a project - Crank, no start, no gauges, weird issues. Help!

[Doubeleive]

Opened the PCM and think I found evidence of a short, but I am not the best at electrical. View attachment 475933

that looks like some very very mild corrosion, probably caused by condensation, you could clean that up easily and spray some electrical contact cleaner all over all the pins, reseat the harness and see what happens.

 

[catalinajack]

Longshot here, but I have twice traced parsitic drains to a bad starter, starters that still cranked. With your battery charged and your engine cold, put your hand on the starter. If it is warm, you have a bad starter. Also, if you have access to a clamp-on ammeter, you can determine whether the battery is supplying power to something and the amperage thereof.

 

[Firebirdracer82]

Update for the day, and I agree with everyone I need a good scan tool. Replaced and programmed the pcm and still crank no start no spark. I’ll be on the lookout for a good scan tool, but for the moment my budget is drained so it might’ve some time.

 

[Firebirdracer82]

Just a recap:

BCM replaced with flashes version to my vin.
PCM same
Both did the key learn procedure and security light is fine.
Crank position sensor replaced with Delphi. Verified voltage and ground (voltage was 8.65v and should be 12v… checked prior to pcm replacement)
Ignition switch replaced, carquest version.
Wiring and fuses all have power.
Cleaned all grounds with and replaced with dilectic grease.
Verified power and ground to coils

I’m starting to suspect it’s the replicator on the crank and the engine is toast. The only sensor I have not replaced is the cam position sensor and that shouldn’t stop it from starting.

 

[Fless]

I'm pretty sure that the 8.65v (as measured at the crank sensor?) is too low; was that measured with the sensor in-circuit? If not, the voltage might be even lower when it's in-circuit. Pick the low-hanging fruit before condemning modules.

Is there 12v at the PCM circuit (under load) and, if so, the 12v feed to the crank sensor may be compromised. You could verify wire integrity by using a test light that draws some current, and could also test it for a partial short to ground.

Circuit shown here:

Engine Controls Diagram 7 — 2004 GMC Yukon/Denali 2WD V8-5.3L VIN T Service Manual | Operation CHARM

Detailed repair manual for the 2004 GMC Yukon/Denali 2WD V8-5.3L VIN T.

charm.li

 

[West 1]

I just read through this whole thread, man, in todays world you start with a good scan tool before doing anything else. They are not always going to find your issue but 80& of the time they will point you directly to your solution. The other 20% of the time they rule out many things to save you time and money. Start with the scan tool. Feed off that and go find your problem.

A scan tool might say: Lost connection to the Crank Sensor. Perfect now you know what might be wrong. Go figure out if it is a bad sensor or bad wires going to it. At least you would have a starting point.

I suspect you have a direct Lost Communications message in your system that a scan tool would read in 5 minutes. Direct failure codes will not clear with a scan tool, these are usually a dead module or a disconnected wire or shorted wire or dead failed part somewhere.
Most codes can be cleared and won't come back till a problem shows up again. Your scanner would not clear your code so something is hard wrong and it is something the computer looks for with every turn key connection.

When using a scan tool on a non running engine you will need to supply 12V power to your car. I use my battery charger set to 25 amp load. It is amazing how fast turning your key to the run position on a dead engine will drain your battery. You might get 15 minutes work time. I was working on an Audi a week or so back and it had constant 25 amp drain when the key was on with the engine off. All the small computers, modules etc fire up and pull large amounts of power in modern cars while testing.

It is my understanding that your age vehicle looks for a crank sensor signal, compares that to a cam sensor signal and then if they match allows the car to start. If they don’t match it goes into a back up system that will take either the cam or crank signal and use it to start but in that case you have extended cranking before it allows a start. Maybe 25-40 seconds of crank time as the computer goes into the back up start mode. I don’t think it will start at all if it does not find either signal from cam or crank sensors. Somebody on this forum can verify that for you.

The scan tool is not what you do when you can't figure a problem out, it is the tool you go to first in these computer controlled cars. Sorry I did not read your post till today and I wish you the very best figuring this out.

 

[Firebirdracer82]

I just read through this whole thread, man, in todays world you start with a good scan tool before doing anything else. They are not always going to find your issue but 80& of the time they will point you directly to your solution. The other 20% of the time they rule out many things to save you time and money. Start with the scan tool. Feed off that and go find your problem.

A scan tool might say: Lost connection to the Crank Sensor. Perfect now you know what might be wrong. Go figure out if it is a bad sensor or bad wires going to it. At least you would have a starting point.

I suspect you have a direct Lost Communications message in your system that a scan tool would read in 5 minutes. Direct failure codes will not clear with a scan tool, these are usually a dead module or a disconnected wire or shorted wire or dead failed part somewhere.
Most codes can be cleared and won't come back till a problem shows up again. Your scanner would not clear your code so something is hard wrong and it is something the computer looks for with every turn key connection.

When using a scan tool on a non running engine you will need to supply 12V power to your car. I use my battery charger set to 25 amp load. It is amazing how fast turning your key to the run position on a dead engine will drain your battery. You might get 15 minutes work time. I was working on an Audi a week or so back and it had constant 25 amp drain when the key was on with the engine off. All the small computers, modules etc fire up and pull large amounts of power in modern cars while testing.

It is my understanding that your age vehicle looks for a crank sensor signal, compares that to a cam sensor signal and then if they match allows the car to start. If they don’t match it goes into a back up system that will take either the cam or crank signal and use it to start but in that case you have extended cranking before it allows a start. Maybe 25-40 seconds of crank time as the computer goes into the back up start mode. I don’t think it will start at all if it does not find either signal from cam or crank sensors. Somebody on this forum can verify that for you.

The scan tool is not what you do when you can't figure a problem out, it is the tool you go to first in these computer controlled cars. Sorry I did not read your post till today and I wish you the very best figuring this out.

100% agree on the scan tool and would love to have one. Looking through marketplace for a tech 2 or something similar but they are out of my price range this month. I’m also looking around for a friend or buddy that may let me borrow one but sadly non of my friends do their own work on cars. I would gladly accept any help around here if anyone has one to borrow. I could get one of the Gearwrench ones from home dept that bi directional but I don’t know if that’s throwing good money after bad. There are also the computer cables people mentioned and I have an old laptop to use if I can find one.

It also comes to that I am not very tech savvy at all but definitely would like to learn.

 

[Firebirdracer82]

I'm pretty sure that the 8.65v (as measured at the crank sensor?) is too low; was that measured with the sensor in-circuit? If not, the voltage might be even lower when it's in-circuit. Pick the low-hanging fruit before condemning modules.

Is there 12v at the PCM circuit (under load) and, if so, the 12v feed to the crank sensor may be compromised. You could verify wire integrity by using a test light that draws some current, and could also test it for a partial short to ground.

Circuit shown here:

Engine Controls Diagram 7 — 2004 GMC Yukon/Denali 2WD V8-5.3L VIN T Service Manual | Operation CHARM

Detailed repair manual for the 2004 GMC Yukon/Denali 2WD V8-5.3L VIN T.

charm.li

I measured the volts at the plug, unplugged from the crank sensor. From my reading it should be a 12v reference.

There is a power drain on the truck somewhere and I am wondering if the power drain somewhere is messing with the voltage to the crank sensor harness.

 

[Fless]

Tell us in what area you live, and look at the Tech 2 owners map to see if someone around you is on that list.

Tech 2 Owners Map

There are quite a few members that have a Tech 2 and there are always people who wish they had one to use so I thought I would post this thread to try and help each other out. If you own a Tech 2 and would be willing to help out another forum member that might be local to you then post up your...

www.tahoeyukonforum.com

 

[Jimmyy]

Make a test light with a tail light bulb and check to see if those wires can carry amperage. A meter can see voltage that can be misleading if there's no load on the circuit. Since you changed the crank sensor, did you clean the mounting point of the sensor. A small amount of rust could keep the sensor far enough away from the magnet not to trigger the sensor.

 

[Firebirdracer82]

Tell us in what area you live, and look at the Tech 2 owners map to see if someone around you is on that list.

Tech 2 Owners Map

There are quite a few members that have a Tech 2 and there are always people who wish they had one to use so I thought I would post this thread to try and help each other out. If you own a Tech 2 and would be willing to help out another forum member that might be local to you then post up your...

www.tahoeyukonforum.com

I’m out in central Kentucky, dint realize there was a map, will check that out!

 

[Firebirdracer82]

Make a test light with a tail light bulb and check to see if those wires can carry amperage. A meter can see voltage that can be misleading if there's no load on the circuit. Since you changed the crank sensor, did you clean the mounting point of the sensor. A small amount of rust could keep the sensor far enough away from the magnet not to trigger the sensor.

I did sadly. But I was on my back in the cold so maybe I’m missing something with it?

 

[Firebirdracer82]

I ordered a "GearWrench" bidirectional scanner - did some research and it was about the same price as a new crank sensor, so I figured it would be a good investment.

I also took the time to add another ground to the coil harness - no change.

I am getting power and ground to the coils, but no signal to them. New PCM, so I am assuming it is either going to be the crank sensor, or a failure to ground on the PCM - assuming G103. I've already cleaned it, but I have not put a new ring on it.

 

[Firebirdracer82]

While waiting on this scanner to come I decided to give the cam position sensor some attention. Interesting and will have to recheck.

I’ve got 12v between the positive and negative with key on, but I also think I’m getting 12v on the reference wire. I will have to recheck this but that’s a bit odd.

Perhaps this is a cam sensor problem, or at least the wires to it.

 

[Firebirdracer82]

Scratch that. I must have had the Leeds wrong or something. Will wait for scan tool.

 

[LsHart]

Okay, so I didn't read thru all of the posts on this topic. But correct me if I'm wrong, isn't the cluster part of the "system"? And if damaged could be causing a power to ground issue or a closed loop that is now open?

 

[LsHart]

Also if it is stock any cam sensor will get a start or try to start condition.i have a Solus and you need to see the data at crank.

 

[Firebirdracer82]

Ok so I used the gear wrench bi directional scanner and came up with these codes. Also see no RPM at crank.

 

[Firebirdracer82]

Here are the code readouts and I possibly found a ground that a rodent chewed but only a bit. I can’t be that lucky. Doubt it made it through the wires but here are the pictures of the code and the wire.

 

[Firebirdracer82]

I started to repair that wire and jumpered it and still no luck. The wire inside looks almost burned.