Car won't start after replacing ECU and electronics failed
Replacing electronic components without disconnecting the battery can cause critical power failures or trigger immobilizer and security systems. This prevents the vehicle from cranking or accepting a charge, leaving drivers stranded with a dead electrical system.
What people tried
Every workaround mentioned in the threads below. We haven’t tested any of them — and nobody here is claiming they worked.
- 1Checking security and alarm systems
- 2Disconnecting the battery during hardware replacement
- 3Buying a good used battery to test if it starts and runs before replacing the alternator
- 4replacing the battery
- 5planning to drive it to the shop
- 6Checking components like the serpentine belt and accessory pulleys
- 7Inspecting the torque converter through the inspection hole for loose bolts or shavings
- 8Towing the vehicle back to the installing shop for warranty or diagnostic work
- 9Getting a multimeter to test the voltage
- 10Fully charging the car battery manually or taking it to a shop
- 11Replacing the alternator
- 12trying tying the battery terminals together thinking that would relearn the new sensors
- 13Using a jump pack to start the car
- 14Replacing the battery alongside the alternator
- 15Bench testing remanufactured parts before installation
- 16Holding the gas pedal down while trying to start
- 17Planning to replace the fuel injectors due to smelling gas on the dipstick
- 18Checking fuel filter or fuel pump
- 19Inspecting for a vacuum leak or re-verifying timing
- 20Jumping the starter relay
- 21Running power on a switch to a wire off the ignition switch
- 22Touching the ground to the column and using a screwdriver to turn it
In their words
Unedited, most upvoted first, each linked to the thread it came from.
“Finally pay day came I put the new alternator on and the voltage is still low coming out of the new alternator.”source ↗
“i really hope so, im going to tear out the alarm tomorrow. i did not disconnect the battery though.”source ↗
“08 Accord, battery light turned on. A day later electronics failed, about a mile later engine failed. Won’t start even with a jump/charge… what now?”source ↗
“So I just need a new alternator or a new battery now too?”source ↗
“2004 Lincoln aviator”source ↗
“engine will not turn, I have attempted to turn the crank pully, no movement either direction.”source ↗
“Really confused about what is going on, really random.”source ↗
“My 2017 Nissan wouldn’t start last Friday, we got a new battery and it started up just fine. I’ve been driving it all week with the new battery with zero issues. Now today I went out on my lunch break and it won’t start again.”source ↗
“Also adding that it wouldn’t start with a jump last week, only started after we put the new battery in.”source ↗
“The battery symbol does come on and all the lights come on it just won’t turn over all the way”source ↗
“I replaced the cam and crank position sensor on my jeep that kept on randomly dying, the code that it had was cam shaft sensor related but that didn’t solve the issue so I replaced the crank sensor as well and now it won’t even start at all”source ↗
“truck still isnt starting this is the closest i’ve been to starting it really tried when i held the gas peddle down.”source ↗
“does anyone else know if it could be caused by something else ?”source ↗
“Today the key wouldn't shut it off. I unplugged the battery and it stalled after about a minute. I just replaced the switch.”source ↗
“A couple nothings, a couple cranks and twice it started for a few seconds and died. I got the tumbler out and hooked up switch again now I got nothing.”source ↗
Where this came up
People with this problem also raised
- 6Car won't start or shift gears after dead battery
- 51Vehicle cranks after fuel pump replacement but won't start
- 6Why does my car lose power for a second when starting?
- 2Furnace won't turn on after new AC installation
- 2Why is my check engine light on after changing the car battery?
- 3Why do ignition coils keep failing one after another?