Wiring and Connections

In my daily travels to shops I get to see some interesting issues. I uncover some interesting wiring issues daily. Some are natural and some are natural with some human help so to speak. I used my human senses and brain power more than my other test equipment to find these issues
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One of my really good customers calls me to tell me he has a 2008 Ford F250 that has an intermittent no crank condition and the customer reports that when the vehicle is in this no crank condition the dashboard has all the warning lamp illuminated.

I arrive and the truck starts and runs like clockwork. This happens all the time. I scan all the modules with Ford IDS and there are many communication codes dealing with the CAN (Controller Area Network) network. A quick scope check tells me the CAN network is operational right now. I look at the modules involved. I see that the CAN wiring runs throughout the vehicle. I give a visual under the hood for anything rubbing or a harness that is not secured. Looks pretty good. I then see the CAN wiring runs down each rocker panel. This truck is definitely a typical Northeast plow truck work horse. I pull up the passenger side sill plate.

Yikes! There is dirt, leaves, and not too much left as far as the rocker panel itself. I literally dig out the wiring harness and surprisingly it is in good shape. I cannot find anything wrong. Well if this side is like this what does the other side look like?

 Just as bad if not worse. I can immediately duplicate the issue as well by moving the harness. You can see the issue barely in this photo. Lets get closer.

Here it is. Between the water intrusion and the dirt it wore one of the CAN wires and corroded it. I repaired this wire and a couple of others. I advised the shop to vacuum out both side sill plate areas. Unfortunately, this will happen again due to the rocker panel area being rotted. The fact that the customer likes to run this vehicle into mud up to the doors multiple times doesn't help at all either.

Next up is a 2012 Toyota Camry that is at a body shop. The owner of the shop tells me that the vehicle was actually in an accident a couple of weeks ago and was repaired at another shop a couple of hundred miles away. Recently, it has developed a couple of strange issues. The vehicles cooling fan runs all the time, headlamps illuminate when not requested, and most troubling is the vehicle will start on its own and won't shut off! The car owners insurance suggested this body shop to rectify the situation. That is when he called me in.

I have been down this road before with these vehicles. In fact there is a TSB from Toyota concerning this issue. I printed it out ahead of time so I could give it to the body shop. I arrive at the shop and the shop owner is reviewing the issues with me. I pop the hood remove the cover from the underhood fusebox and I am greeted by the unmistakable smell of burnt electronics. As the owner is talking to me I wiggle up the Integration Relay in the underhood fusebox.

That is a hole burnt right through! Now the whole shop has the burnt electronics odor emanating throughout. The body shop owner lets out a couple of descriptive expletives and calls everyone over to look at the relay. Next lets look at the wiring.

That bare wire in the photo is not supposed to be bare. The heat from the amp load burnt off the insulating jacket and left a bare conductor. The reason is carefully laid out in the TSB. The vehicle grounds are attached to a support. Typically, a body shop will undercoat or paint these supports and often times insulate the grounds causing a voltage drop. The TSB wants you to expose the support sand and use new redesigned bolts. But, we will still need a underhood fusebox, some wiring, and a new Integration Relay. I leave the TSB with the body shop to use as a guide.

Next is a 2004 Dodge Ram Truck that the owner said just died out and now is a crank and no start. The shop checked for PCM communication and had none. They also check for spark and had none. I arrive and confirm the no communication with the PCM. I check for proper 5vref and have a strange fluctuating voltage that never reaches 3.0 volts. Ok, maybe I have a sensor that is loading the 5vref line down. This is pretty common. A couple of minutes later all sensors on the 5vref line have been disconnected and I still don't have a solid 5vref. Lets check powers and grounds at the PCM. I pull a wiring diagram and verify proper powers and grounds. Did this PCM go bad? Looking that way. I have been burnt before with JTEC terminal tension. I pull the PCM connectors to do a pin drag test and quickly see my issue.

That green spot is supposed to be a terminal. A terminal that supplies power to the PCM. Where is the terminal?

There it is stuck in the PCM connector. Now, this vehicle is going to need a PCM and I am going to have to do some micro surgery on the PCM connector and replace that terminal. The terminal that rotted is at the bottom of the PCM. Somehow, water got into the PCM harness and laid there and rotted that terminal out. In talking to the owner this vehicle was in an accident years ago and sat for a long time before he bought the truck. probably with the hood off. Maybe then?  

I have had quite a few emails lately. I will be answering them all real soon.

2000 Nissan Maxima

One of my shops calls me and says that they have a 2000 Nissan Maxima and its a crank no start. I arrive the next day and I see a very clean Maxima with 75,627 miles on it. I reach in and it cranks strong with a good cadence. But, it doesn't even hint of starting. Time to get some information. I quiz the shop owner who tells me the vehicle belongs to a gentleman that spends extended time out of the country at times. He left six months ago and the vehicle was running. Ok, now we have some information. Right away I am thinking rodent damage. Mice and the like love to crawl up into vehicles and chew on wiring. I perform a thorough visual inspection and no obvious signs of rodent damage.
I hook up my scan tool and check for codes and I have a P0335 code for Crankshaft Position Sensor. I also have no cranking rpm on my scan tool when I am physically cranking the engine over. Now at this point some background on this system. This Nissan platform is very common in my area and I have a lot of experience with these vehicles. This year Maxima has a CKP (POS) that reads off the flywheel and is mounted in the oil pan adapter. A CKP (REF) that reads off the front crankshaft dampener. A CMP (Phase) that reads off the Bank 2 Camshaft gear. This setup described is for a 3.0 Liter VQ30DE engine. Now there are some variables. There are two different crankshaft dampener setups. This will alter the CKP (REF) signals. I forget the years off the top of my head that are different. I have many known good patterns from many years on this platform. I just compare to a know good in my library of waveforms.
Typically, if any these sensors are not reading or reading correctly you will get a crank no start. There have also been issues with grounds, revised starter motors, starter motor RFI while cranking, Usually when there is a ground or starter or RFI issue the vehicle will crank erratically almost like a vehicle with a wet distributor cap. This vehicle cranks smooth. Furthermore, I have seen timing chain issues cause a P0335 no start. Time to hook up the scope.

  
So, here is the a shot of this vehicle cranking with the Pico scope hooked up. This is just a saved screenshot. With the Pico I can save a file with a tremendous amounts of data. Furthermore, I can manipulate the file how I wish afterwards. So what I see here is the correct CKP (REF) pattern for this year and it looks like the CKP (REF) and CMP (Phase) are in proper alignment. What I see wrong is an almost non existent CKP (POS) signal. The CKP (POS) is a hall effect square wave signal where the REF and Phase are inductive AC voltage signals. With this I test powers and grounds at the CKP (POS) connector. All good there. Has to be a bad POS sensor. But, how did a sensor go bad in six months of sitting? I always recommend an OE sensor but due to time constraints an aftermarket sensor was ordered. I installed the sensor as the shop owner was busy and went to fire it up and still no start and this time I didn't see any activity on the POS sensor signal now. Sorry, don't have the scopeshot. I was to busy cursing and screaming. I took a breath and popped the aftermarket sensor out and waved a knife blade across the tip of the sensor with the key on simulating the flywheel teeth and saw nothing on my scope. I reinstalled the original sensor and repeated the knife blade test and had activity. I had a theory now.

    
The sensor mounts to the aluminum oil pan adapter. I made sure there was no obstructions first. This time around I noticed quite a bit of oxidation in the POS sensor mounting area. I grabbed some sandpaper and scrubbed the area thoroughly. Hit the the area with a little brake clean and popped the original sensor back in. I hit the key.

  

The vehicle roared to life and ran well. Now, I had POS signal. Let's zoom in a bit.

Let's zoom in even more. The Pico has excellent zoom and resolution qualities.

Now, you can see the POS signal clearly. I tried the vehicle several times it always started very crisply and the waveform was excellent throughout the temperature ranges. I cleared the code,

Here is the actual piece of sandpaper I used with the oxidation on it. The fastener in the picture is one of the screws that hold the cover on underneath the vehicle. The theory here is that the vehicle sat and the oxidation occurred forcing the sensors air gap to increase. I have seen this before on Nissan vehicles with ABS wheel speed sensors. The aftermarket sensor was bad right out of the box. Having worked with these type of sensors in a lab setup I have seen the slightest change in air gap mean the difference between a signal and no signal. Reminds me of a Maxima I checked out a couple of  years ago for a shop that was a crank no start after an engine replacement. Long story short the shop never swapped the manual transmission oil pan adapter that came with the used engine (where the CKP (POS) mounts) to the vehicles automatic transmission one. The result no CKP (POS) signal because the sensor was too far away. That shop never made that mistake again.

Mailbag

Have received some emails lately. Here is one from Charles Smith.

Title: 2003 Chrysler PT Cruiser P02302

Working on a friend's car, someone else has already changed the plugs, wires, coil and cam sensor. Misfires on cyl. 2 after warm up. But still getting a good spark from coil on 2. Turning off the key and restarting, Engine runs good again for a short time. I'm thinking the pcm has a bad quad driver and is shutting down the injector. What are your thoughts. I'm leaning towards a pcm replacement.

Actually this is a P2302 not a P02302 just to get logistics correct. P2302 is a Coil #1 Insufficient Coil Ionization code. This is a very common code with Chrysler products. The poster didn't leave a VIN or description of engine size or turbo or non-turbo. Either way these vehicles utilize a coil pack design. There is actually two coils so to speak in the one pack. Coil #1 fires cylinders #1 and #4 and Coil #2 fires cylinders #2 and #3. The PCM contains an algorithm that can infer monitored burn time of the secondary pattern to set this code.

A couple of observations. The poster states that it has a misfire on cylinder #2. Yet, the code is for Coil #1 which is cylinders #1 and #4. P2305 would be the Ionization code for Coil #2 which is cylinder #2 and #3. I have seen some cheaper aftermarket scan tools give incorrect codes and code definitions.

When the poster says "good spark". What are we talking about? How are we testing? Scope? Test plug? Adjustable gap style tester? How long it takes for his hand to stop tingling? We need some specifics here. Any late model ignition system should be able to jump a 7/8" gap with a nice white blue consistent spark. 

The poster states someone else changed various parts. Were they OE? I am a big believer in OE ignition parts especially on Chrysler products. There is a difference. I open up the hood on some of these problem vehicles I look at and it looks like the local auto parts chain store threw up into it. When I tell the shop its has a bad coil I usually get "It's new". I tell him/her new doesn't mean good.

Turning off the key and it runs well again for a short time. The PCM is taking out injector pulse when it sees a catalyst damaging misfire on that cylinder. This is perfectly NORMAL. It will discontinue operation for that key cycle. What the poster is experiencing is normal strategy. Fix the misfire and the injector pulse will continue uninterrupted.

Quad drivers is an old GM expression back in 80's when we had quad driver codes. Some Saturn vehicles used quad drivers into the 2000's. This would be a regular driver.

My recommendation to this poster is to recheck codes with a professional scan tool. Replace said replaced parts with OE parts for starters. If it still acts up then we would have scope the primary and secondary patterns. A thorough harness check. There is a very good chance that the PCM is at fault. Usually from degraded secondary ignition components. Now, if we have to go with a replacement PCM. Well, that is always an adventure with remanufactured units. Look at some of my posts. 

Charles, let me know how you make out and if I can help you out anymore.

Off The Grid

Yes, it has been some time since I have posted. I have been super busy and been neglecting my blog. I promise to have some more content up very soon.

In the meanwhile. I just want to wish a very Happy New Year to my crew throughout the country. Those of us that battle problem vehicles on a daily basis. I wish nothing but the best for the coming year. I am grateful to be surrounded by some very good people in the industry from all over the United States and Canada.

Speaking of good people I want to take a moment to acknowledge a good friend of mine Dave Macholz. Dave is an automotive instructor at Suffolk County Community College. He recently has received a very well deserved promotion. The automotive program he is involved in is top notch and will only get better with him steering the way. In addition Dave has been writing in the trade magazines and is a training instructor for WorldPac. Having attended a Toyota class Dave did last month I can attest to the quality Dave is presenting. Hopefully, in the next couple of months Dave and I can collaborate on some local training.

Also take a look at my buddy Mike's website www.advancedmobilediagnostics.com

Mike and I work the same region and sometimes the same shops. We respect each other and each others business. We talk to each other every day and bounce ideas off of each other often. Never can have enough good people that is for sure.


Be back soon