Circuit Integrity

Hello All-

I recently watched a video where Paul was testing the integrity of a sensor signal wire using a T-Pin and test light. Very, very informative for someone who is learning this stuff. The question I had which might sound simple to many of you is this-

Can this procedure be done on other wires and not just the signal wire?

I highly recommend for newbies to check this video out and if you have crappy internet like I do, take a pen and paper out and take notes- this way you can make your own diagnostics binder as a quick reference as I am doing. Thanks Scanner Danner for all these videos-

Mr Mike

In the general sense, there are many other circuits that can be tested for integrity with the test light/T-pin combination. Outputs are a prime example. Were there specific circuits you were thinking of?

The trick comes with careful use of the T-pin (to make sure you don't short across circuits) and making sure the load of the test light is appropriate for the circuit being tested.

Hey Tyler-

I dont have anything I need to try it on, but was just wondering because in the video Paul was testing the signal wire and I did not know if the same proceedure worked for like the Ref and grounds-

Thanks

MrMike wrote:

I dont have anything I need to try it on, but was just wondering because in the video Paul was testing the signal wire and I did not know if the same proceedure worked for like the Ref and grounds-

I gotcha. In the case of a sensor reference circuit, an incandescent test light would not be a good choice. :silly: All it's gonna do is short the reference to ground, set a ton of codes and piss off whatever module supplies the reference.

Sensor grounds *could* be checked with a test light? But it wouldn't be my first choice. The sensor ground circuit in the module being tested might be able to handle the current of a test light, or it might not. I'm more comfortable sticking to voltage drop instead.

Tyler-

Thanks for the clarification. I have a computer safe test light, but after what you said, I am going to use the test light on other stuff and stick with my trusty Fluke for the other stuff. I wanted to copy and paste some issues in this thread about my truck. When you have some time, could you check back and read it and maybe give me any suggestions? I would greatly appreciate it.

Thanks,
MrMike

2010 Dodge Ram 1500 (5.7) HEMI

A few months back, I was having intermittent starting issues- meaning that sometimes the truck would start right up and other times, I would have to keep the key turned to run/start for anywhere between 15-45 seconds before it would start? I checked the Batt(+) cable going to starter and was getting proper available voltage to the starter. Also verified the Batt terminals/clamps were clean like newborns baby butt. When it would start and Id drive a small distance and turn the truck off, it would not start again, but would if I hooked up jumper cables? I checked Batt volts and was reading around 12.6V. I was getting the "Red Lightning Bolt" on the dash, so I hooked up my scanner (Autel MaxiSys) and got a code P0123 or bad throttle body. I researched this before I even new Scanner Danner existed and everything says to replace the throttle body. I replaced the throttle body (I know) and same thing. Then people say its the WIN (wireless ignition node) which is not wireless because it has a small 12 pin connector on back with just 8 wires. I took off the WIN ignition key box and opened it up- the small contact arms looked good, so I went ahead a got a q-tip with rubbing alcohol to clean what I could just to be on the safe side- still no difference. Out of curiosity one day, I got under the truck and had the wife turn key to run- No power at starter solenoid? I Ohm'd out the Yellow/Grey wire from starter relay- it was good. I also bench tested the relay with a 9V battery- it was fine-(clicking). I have since torn apart the dash and cleaned up any grounds I could find to include engine and chassis grounds. My next step is to check the starter relay sockets in the TIPM to see if they check out. Also, if Im not getting the volts to the starter solenoid, Im thinking it could be the Neutral/Safety switch which Dodge calls the Transmission Range Selector which I have not tested yet. I dont want to assume anything because I did push ups years ago in the military for using that word.

Im somewhat stumped but am convinced it is probably something very simple. I have the complete wiring diagram from Mitchell and also a downloaded "Shop Manual" supposedly the dealerships use. The shop manual stated that after replacing a throttle body, use a scan tool to do a TPS/Throttle Body Re-learn but my Autel scanner does not have this function.



Update: I started checking continuity and their is an OL between MAP Sensor 5V Ref and PCM (weather has been bad and I have not looked for the break yet)

I need some guidance on this please. Any info/recommendations you could give would be greatly appreciated.

Thank You Sir, in advance-
MrMike

Have you tried putting it into neutral and cranking when it gives you the intermittent no start? I have a 2008 dodge caravan. Having the same issue every now and then. And when I put it into neutral it fires right up… I will also say this, I only have this issue when my Tipm is losing connectivity in one of the harnesses underneath.. I’ve narrowed that down ultimately with a wiggle test..(long story I won’t bother you with) but I’m gonna throw an amp clamp around the Tipm (+) cable and (with the car running) I’m gonna wiggle those wires one by one while watching my scope for any drop outs.. In theory it sounds good. But we’ll see…
Chrysler really dropped the ball on these years of the Tipm, who knows? Problem may also lie within your tipm also…? But good luck man I hope you get it diagnosed..

Hey Jjclark-

Thanks for the response. Going back, I re-tested the MAP wire and it is good. I think when I initially checked it, the probe pin at the PCM harness was not getting full contact, thus the OL reading. To answer your question, I have not tried to start it in neutral yet. I just got the intake manifold, fuel rails and injectors in place today. Tomorrow, Ill get the throttle body, vacuum lines and charge battery, then see if it will start in neutral. Ill let you know what happens. Are your TIPM connectors the Tyco ones? And I thought Tyco only made slot cars- haha haha. Yeah- I've heard of other Dodge owners have had electrical gremlins with certain year/make/models. You would think it would be more user friendly. Ill let you know tomorrow what happens. Thanks

So- earlier today, I hooked everything up and charged the battery. Went to start it, and nothing- not even in neutral. I noticed that the dome lights inside did not dim at all when trying to start. I think tomorrow I will check the fuse and relay feed for the starter solenoid and see what happens. Any suggesstions?

courses.handsonautotraining.com/courses/...&utm_source=hs_email
I just finished watching this video about a Ram with a very similar intermittent no crank, that would some times fire up if the ignition was left on.
You may have to sign up for a free membership to view the video.

Thanks Noah-
Ill look into the video. I'm hoping this is something simple I can fix at home.

What's interesting about the video is he talks about the trailer brake control module. When I bought the truck, it had an aftermarket trailer brake control the previous owner had installed. Well, I had cut that off the control at the wires the other month. I wonder if this has anything to do with it? Very interesting

I just thought that the symptoms sounded similar, I have never run into one that would eventually crank if you left the key on, and then I read about two in the same day! (Yours and his that is)
Does yours have communication to the PCM when it doesn't crank?

Im by no means, no expert at this stuff. I have the digital Mitchell wiring diagram and going to look at it. Can I check the coms to the PCM with a DMM? I saved the old brake controller that I snipped off and if it does not rain today, Im going to use heat shrink butt connectors and hook it back up to see what happens. I will definitely let you know what I find out. Thanks-

If you can read codes and data, then the PCM has communication, no meter or scope required (yet)

Ok Noah- I should have comms- last time I hooked up the scanner, it showed data. So, today I hooked up the old electronic trailer brake just to see if she would turn over- No Dice. This may be nothing, but I kept the key turned on start position for around 30 seconds or so and I heard for maybe a second, the starter pinion gear engage and release, but still no start. It then decided to rain, so I went inside. Im trying to figure out my plan of attack for either tomorrow or Friday depending upon the weather. I think the first thing I will do is disconnect all TIPM harnesses under the fuses and take a real close look at the pins and harness cavities. Its simple and might rule something out.