Voltage Drop: Multiple Symptom Disorder — 2003 Corvette
Customer drove the vehicle in. Customer states that the driver's headlight is up and the passenger side is down. It appears that the running light is on and the instrument clusters turn signal indicators are solid on. Inspect and advise on repairs. The customer has had this problem for some time and is very intermittent.
NOTE***If the vehicle is shut off the symptom usually goes away.
The data above was how the service ticket presented the vehicle to the technician.
Notes directly from the service ticket as presented by the technician:
Perform system scan, vehicle is loaded with several DTC's. Perform system checks. Visual inspection revealed a loose Batt negative cable. Perform lighting system tests and validated failures. Perform circuit checks and Isolated the issue to G102 - loose, poor ground. See video summary demonstrating 1.2v - 3.1v while moving terminator. Dissasemble and inspect. Clean and install star washers and new nut. Recheck V drop on with system loaded and found .001v = normal.
Vehicle has other issues:
- ABS/Traction control warning messages appear when the hazards are switched on.
- Brake lamp circuit code needs to be addressed.
- 3rd brake lamp is inop.
- Battery hold down is loose, wrong battery installed
Scan all vehicle systems and retrieved the following:
- B2578 FR TS Monitor Circuit Short High
- B2583 LF TS Monitor Circuit Short High
- P1539 AC Clutch Feedback Circuit High
- B2204 Driver Window Down Sw Fault
- B2206 Driver/Pass Window Up Sw Fault
- B2208 Driver/Pass Window Down Sw Fault
- B2282 Driver Clean Battery Fault
- B2284 Driver Dirty Battery Fault
- U1016 PCM Serial Data Fault
- U1064 Lost Comms with BCM
- U1255 Class 2 Serial Data Fault
- U1096 Lost Comms with DIC / IPC System
- B2283 Passenger Clean Battery Fault
- B2285 Passenger Dirty Battery Fault
- U1064 Lost Comms with BCM
The next section breaks down how we addressed the issue which I hope helps someone else who may be presented with a similar challenge.
Time to develop a strategy and see if there are any single failure points that could result in any of the symptoms exhibited and or DTC's stored.
Since the headlights were the main complaint, I decided to take a look to see how they work. SI was consulted for operation and any details about power distribution. But before I go too deep, I paused and decided to visually inspect for any clues and I found one, a faulty battery install with loose cables. Re-securing the cable connections had no effect on the headlamp operation.
Back in SI and looking a little deeper, it was noted that Splice Pack (SP100) connects at G102 and that's where we found and verified the issue by testing voltage drop between B- and one of the splice pack feed wires. This connection is located on top of the right frame rail a few inches rearward of the radiator fan shroud mounting supports.
I assembled a short video detailing this event which I hope can help someone gain some additional knowledge on the importance of measuring voltage drop.
Scott, Great case study. Voltage drops can be killers, especially in splice areas. I know they've driven me nuts before, so it is always good to revisit and remind yourself how important the test (and understanding the results) can be. What intriqued me more than the case itself though is the section from the service ticket that said "See video summary demonstrating 1.2v - 3.1v while moving
Thanks Chris. The SMS (Shop-Ware) we use in our shop allows us to share video, photos or any other media to help support a service visit. All customers have access to their service records and we often converse with the client virtually through the service ticket.
Chris. At our shop (I work for Scott), we strive to give customers the most bang for their buck. Every technician, all the way down to the lube tech, add pics and videos to all work orders. It adds value to the the write ups we do on work orders. Every detail is explained and backed up with visual data that shows the customer every step we took to properly diagnose and repair their vehicle…
That is an awesome system and something I wish I saw more of. I've utilized the same processes for years on my own, but not with a comprehensive program. Documentation is key. I'm thrilled that your educating customers to that extent. It is an important step for our industry. If I ever break down out in California, I may just have to give the job to Scott and your team.
Scott, A Corvette with a bad ground causing multiple issues. Say it ain't so. Lol. A great example of divide and conquer. When faced with multiple issues pick one and go for it. A lot of times the dominoes will fall afterwards. Do you have any scope shots of Class 2 while wiggling that ground? Nice work and love the video work pretty impressive.
Hi John, Negative on the captures as the scope never came out on this job. Perhaps next time though. Thanks for the feedback on the video, I appreciate your comments.
Wow, you guys running a shop or a movie studio?!? :-) It would take me forever to find it, but I believe GM had a bulletin "back in the day" that if you had a bajillion DTC, ALL in History, you should never chase them, just go tighten the battery cables and start over. (or something like that) That improper battery installation made me laugh because EVERY car is like that here, I even know
:-) NAPA is the only place less than one hour away, so 728031 is the # I know.
Hello Scott, I enjoyed your presentation. What program have you used to create that video? Thank you
I keep teaching myself iMovie then forgetting everything by the time I go back to it again. Sort of like learning early 2000 Toyota EVAP or the Chrysler LDP system. As soon as I "get it" it's two months before i see it again and then it's like "wtf?" (again).
You have to do this routinely or it won't stick... Get in the habit of shooting something with your cell and then import it later into a project and crank something out. Let me know if you have any questions, I'm happy to assist.
You're busy enough! :-) There are many good youtube videos I have bookmarked. Just have to remember to watch them. Thanks Scott