I can feel the tension!
This weeks topic we are going to discuss circuit integrity by way of pin tension. Sometimes when you check a circuit, everything seems good so you start scratching your head with the “why am I having a circuit issue then”. A lot of times when you have an issue like this it has to deal with pin fitment and pin tension. When I use the term pin fitment, I am referring to the male portion of the terminal and if the male portion is oriented correctly or inserted all the way. When you hear the term pin tension it generally refers to the female side of the terminal and it describes how loose or tight the female terminal is on the male pin. You might not think that a slightly loose pin tension can cause issues but believe me it can and it will. There are different ways of testing the tension. The most common way it to use a male terminal and insert it in to the female terminal, and see how it feels when you insert and remove it. It’s difficult how to explain the way it should feel with out an example, but the easiest way is when you insert or remove the male pin you should feel a slight drag of the female terminal as it slides. If the terminal is loose you either won’t feel the dragging sensation, or the male pin will feel sloppy when inserted. (if you were able to get through the past couple of sentences with out laughing you’re a better person than me) Another technique is pretty much the exact way I just stated but you’re using an actual terminal tension tool. Generally this tool comes in a set with different sized terminals and is slightly weighted. When you are doing this check you insert the terminal tension tester in to the female terminal and let go of it. If the test tool stays inserted theoretically your tension will be good. The plus to using this, is it will give you a more accurate test. I have a case study I did this past week that dealt with pin tension and it causing multiple issues. I was called out to a shop to diagnose a throttle position sensor hard fault. The shop had already replaced the throttle body, pcm, and checked the ohm’s of the harness from the throttle body to the pcm. When I got there I performed my initial code scan and found the throttle position code, then quickly pulled up PIDS for the system to see what all the PCM was seeing. The first thing that caught my eye was the TPS1 was reading 5v when it should have been reading close to 2.5v (per the service info). Usually when a circuit like this is reading 5v, the signal wire is open. So I used my oscilloscope and tapped in to the signal wire for TPS1 and the voltage at the sensor was reading properly. So I decided to disconnect the PCM connector to check pin tension/fitment and integrity of the signal circuit. This is when I found the pin tension was extremely loose. I should note also that the PCM connector was in very poor shape and the locking mechanism was broke. But I was able to adjust the pin tension on this terminal, put it all back together cleared the codes and everything started reading properly for this circuit. I left and then was called back out the next day for the same vehicle separate issue. This time the vehicle was randomly shutting off while driving, randomly not starting, and randomly misfiring while driving. When I got there I pulled codes and the PCM had 27 stored codes from cam/crank codes, misfire codes, and many more. So I decided to go straight to the pcm connector, and with the vehicle running I could wiggle the connector and get the vehicle to misfire or even stall out. So I pulled the connector off and found pretty much all the pins where having tension issues. (hindsight I should have checked this when I was there the previous day. But I didn’t have issues with anything else) So at this point I recommend the shop either replace the connector (which had roughly 110 pins) or replace the main engine harness. All of these issue came from pin tension issues and no hard faults to the vehicle. So with all this said, get in to the habit of checking pin tension anytime you remove a connector. Not only will this assist you in your diagnostic strategies, but it will also greatly reduce you chances of come backs.
