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My car was behaving strangely recently. Sometimes when I gave it the beans it would pop up a flurry of scary error messages about the engine, that I had to take

My car was behaving strangely recently. Sometimes when I gave it the beans it would pop up a flurry of scary error messages about the engine, that I had to take it to the mechanic to have it checked out and so on. 500 € later and the mechanic could not fix the issue. Other times, just turning on the engine it would complain that some filter was almost full. And once, on a longer than usual trip, it gave up on me in a pretty steep incline and I had to stop on the side of the road, let it cool down a while, and turn it on again and it worked mostly fine if I didn't accelerate too much. Then a few weeks ago it did not start at all. So I measured the battery and it turned out it was toast. I had a friend bring me to buy a new one and swapped it in. The car started fine. But incredibly, it never again displayed any error messages and seems to be completely fixed! Not really phone related, but yeah, sometimes it can be (surprisingly) just the battery...

s0rce 5y ago
When my cars give funny messages, or struggle to start (more obvious), if the battery is old (5+ years), I just replace it. Its a $100-200 and I can do it myself, better than paying a bunch of labor to troubleshoot ghosts and its up for replacement anyways. If the battery is new then its a bit trickier, but so far its often been just a battery issue.
sandworm101 5y ago
This is why diagnosis equipment always tracks voltage. Most sensors rely on voltage tied to some sort of variable resistor. If your battery/alternator is sending high/low voltages then those sensors will send false readings, leading to any number of random error codes. Put a multimeter on your system and check for any departure from the 12v standard (actually 13.8v) during operation. If so, replacing the battery is a good first step. If your voltage is steadily above 13.8, then your regulator/rectifier is fried. Swap it out before it starts cooking your battery.
- jandrese 5y ago
  The caveat of course is that battery measurements are only good if the battery is under load. I had a dead battery that was confounding me because every time I measured it the battery would show 13.5v but then the car wouldn't crank. This is why shops have battery testers with a big resistive heater on the bottom. The good news is you can diagnose this with a pair of jumper cables easily enough. In general though electrical problems are the hardest to track down, especially when it turns out to be a corroded or missing ground strap somewhere.
  - axiolite 5y ago
    No need for special equipment. You can diagnose a weak battery just by turning on your headlights.
    - genocidicbunny 5y ago
      I'm not sure this is true anymore with recent cars. Mine has LED headlights and turning them on barely drooped the battery voltage. If you have someone who can help, measuring the voltage while you try to start the car can help more directly diagnose this.
gamacodre 5y ago
Sometimes it's the battery (system) even when the battery is fine. My son spent something like $1200 chasing the ghosts of electrical issues in a Ford Expedition with multiple mechanics. And they did in fact replace the battery at some point in there, to no avail. It turned out that one of the battery _cables_ was bad; enough corrosion had built up under the insulation that the voltage would do all kinds of strange things depending on the exact load on the system. $20 for a new cable fixed it all.
- voakbasda 5y ago
  I had the same problem after refueling once. Car had been running fine for hours and suddenly would not start Turned out to be a bad ground connection. Fixed it on the spot with a wire brush to remove the corrosion and rust.

s0rce 5y ago

When my cars give funny messages, or struggle to start (more obvious), if the battery is old (5+ years), I just replace it. Its a $100-200 and I can do it myself, better than paying a bunch of labor to troubleshoot ghosts and its up for replacement anyways. If the battery is new then its a bit trickier, but so far its often been just a battery issue.

sandworm101 5y ago

This is why diagnosis equipment always tracks voltage. Most sensors rely on voltage tied to some sort of variable resistor. If your battery/alternator is sending high/low voltages then those sensors will send false readings, leading to any number of random error codes. Put a multimeter on your system and check for any departure from the 12v standard (actually 13.8v) during operation. If so, replacing the battery is a good first step. If your voltage is steadily above 13.8, then your regulator/rectifier is fried. Swap it out before it starts cooking your battery.

jandrese 5y ago
The caveat of course is that battery measurements are only good if the battery is under load. I had a dead battery that was confounding me because every time I measured it the battery would show 13.5v but then the car wouldn't crank. This is why shops have battery testers with a big resistive heater on the bottom. The good news is you can diagnose this with a pair of jumper cables easily enough. In general though electrical problems are the hardest to track down, especially when it turns out to be a corroded or missing ground strap somewhere.
- axiolite 5y ago
  No need for special equipment. You can diagnose a weak battery just by turning on your headlights.
  - genocidicbunny 5y ago
    I'm not sure this is true anymore with recent cars. Mine has LED headlights and turning them on barely drooped the battery voltage. If you have someone who can help, measuring the voltage while you try to start the car can help more directly diagnose this.

gamacodre 5y ago

Sometimes it's the battery (system) even when the battery is fine. My son spent something like $1200 chasing the ghosts of electrical issues in a Ford Expedition with multiple mechanics. And they did in fact replace the battery at some point in there, to no avail. It turned out that one of the battery _cables_ was bad; enough corrosion had built up under the insulation that the voltage would do all kinds of strange things depending on the exact load on the system. $20 for a new cable fixed it all.

voakbasda 5y ago
I had the same problem after refueling once. Car had been running fine for hours and suddenly would not start Turned out to be a bad ground connection. Fixed it on the spot with a wire brush to remove the corrosion and rust.