Quick question

My Insight CTS seems to be giving me inaccurate voltage readings when running. About 2 weeks ago I replaced the alternator on my truck due to low readings, had it tested and it was bad. Now my CTS is showing volts when running between 13.2 and 13.8 fairly consistantly. When I got home yesterday I parked the truck and I was showing 13.5v on the CTS. I got out my handy multimeter and tested the volts and the batteries and both read 14.1v. I have read that that due to loss in wiring and connectors that and gauge could read as much as +/- 5% which would make my CTS reading correct. Just makes me wonder what other readings on the CTS are inaccurate.

Any thoughts? Thanks in advance

 

Loss in wiring and connections may not reflect the voltage at the batteries, but the readings may be reflective of the voltage at the components due to loss in wiring and connections.

There will always be some drop in voltage, but the goal is to reduce those drops by improving connections, cleaning any that haven't been touched in years. What is the voltage at the power port? Is it close to that at the batteries?

 

Not sure what you mean by "power port"??

 

Both my edge and my SCT Livewire read about a half volt Less that actual batt volts. The OBD port volts are often lower than the the battery, nothing to worry about.

 

Kind of what I thought, just wanted to ask the question.

Any reason to worry about other readings with a CTS? None of the numbers seem out of the ordinary but just wondering?

 

Does it really matter? There's no reading you can get from the PCM that has to be so accurate that the cumulative errors the components really matter. I bet most of the sending units themselves aren't better than +/-3%, they don't need to be just to make sure coolant at the t-stat housing is within 5* of 190*f. Consistency over the long term is more important than if a single PID is highly accurate.

The 12V plugs on the dash, one is a cigarette lighter and the other just has a plastic plug stuck in it.

 

I will check the power port at lunch just to settle my curiosity.

 

Wanna bet that your last alternator wasn't bad after all. You Must test not only at the batteries, but at the rear post on the alternator for the most accurate reading due to line resistance.
I see the same 13.5 v on my Dashboss through the OBD port, approx 1/2v diff.
Hope the forum can save you a few bucks in the future.

 

That is definitely a possibility. On the last alternator the CTS read low 12's and with engine running it read mid 12's at the battery. To compound everything my FICM was reading in the low 30's when driving so before I fixed the FICM I put an alternator on it. When the CTS was a little low on the Batt volts I started checking everything to hopefully prevent frying another FICM. Both batteries test good when cranking. Looks like I can check this off my to do list....for now...

 

Work in progress, posted before. About as good as your going to get.