Q: Check engine is on after new alternator

asked by on June 30, 2017

So I get a new alternator and battery. Now check engine light comes on as I'm leaving the shop. I go back to mechanic, he said something about rpm read and memory. Whatever. He gets engine light off. I go get gas. As I'm driving away, car stalls. Engine light comes back on. I turn the car off and on again and it drives halfway home before it stalls completely again. Battery AND check engine light come back on. Turn off for a minute and starts right back up again. Does this 5x before I get home..... HELP this was all in about 15-20min

My car has 114000 miles.
My car has an automatic transmission.

Battery will not hold a charge Inspection $94.99 - $114.99 Get a Quote

It sounds like you may have a failing voltage regulator. When the voltage regulator is not working properly, this may result in the alternator allowing too much power to be delivered to the battery resulting in damaging wires and prematurely sometimes destroying the battery. In other cases it may result in the alternator not supplying enough power to the battery, resulting in undercharging the battery or not charging it at all. In some cases when a battery is too weak or damaged, it may no longer hold a charge for any length of time, in which case the alternator may be doing its job, but the battery is just simply too weak to hold a charge. In either case, I would recommend having an expert from YourMechanic come to your location to diagnose your vehicle’s charging system.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing


Experienced Mechanic?

Earn up to $70/hr

What others are asking

Car leaks antifreeze from hose
Coolant leaks can be tricky. I recommend having a certified technician, such as one from YourMechanic, come out to your car's location to run a diagnostic inspection of your antifreeze leak (https://www.yourmechanic.com/services/oil-fluid-leak-inspection), and suggest the best path to repair.
After installing new spark plugs they soot up after 70 miles
High mileage engines leak oil into the combustion chamber through worn out valve stem oil seals, worn valve guides and ill fitting piston rings. If a substantial amount of oil is entering the combustion chamber the plugs will quickly foul....
Hearing clicking from wheel housing while turning
Hi. A clicking noise while turning in a front wheel drive car is usually caused by damaged or worn CV joints (https://www.yourmechanic.com/services/axle-cv-shaft-assembly-replacement). CV joints are mounted on each end of a front axle and they transfer power to the wheels...
Brake lights stay on 2000 Chevrolet Silverado 1500
Hi there - I believe your brake light switch (https://www.yourmechanic.com/article/symptoms-of-a-bad-or-failing-brake-light-switch) is either sticking or mis-adjusted, resulting in the brake lights remaining on after the brakes are used. Turning the ignition switch to the "Off" position removes power to that circuit,...
I have an error code P0441. It is recommended that I replace the purge control valve. Where is this located and how do I replace?
Hi there. The purge control valve on your vehicle should be behind the engine air filter housing. You may have to remove the air filter housing to get to the purge valve. The valve is held on by a couple...
What is the cost of a cylinder head replacement and is this reasonable?
Before having the cylinder head replaced, check the compression on all cylinders. What you are looking for is that the compression is 120 psi or more and the first puff of compression is half of the max puff of compression....
D light blinks and gear stuck onto neutral although its geared to D or R. What is the problem of my honda crv 2003?
Hi there. Unfortunately, without being there to complete a gears are difficult to change inspection (https://www.yourmechanic.com/services/not-able-to-change-gears-inspection); any guesses on what's causing this problem would simple be a guess and not very responsible on our part. It could be something as...
I have a Subaru Impreza 2009 and the two charger ports do not work as aux and there is no aux cable input even though the radio aux.
Check the fuses with the auxiliary charging ports to see if they have burned. If the fuse is good, then there is an open or short within the wiring to the charging ports. The radio has an auxiliary wire attached...
Reduced engine power, service traction system, traction control off on my 2006 Buick LaCrosse
Hi there. Though there are a lot of reasons that this can occur, most of the time it is because of a voltage issue. I usually make sure that the battery cables are good and that the ignition switch is...

Related articles

2012 Honda Odyssey vs. 2012 Mazda 5: Which One Should I Buy?
Passenger vans may be one of the most maligned classes of vehicles. From being called "Mom-mobiles" to being mocked extensively by those who have not experienced the comfort and ease of getting into and out of a van, vans just...
Mazda Certified Pre-Owned (CPO) Car Program
If If you have been shopping for a used Mazda vehicle, you may want to check out cars under their certified pre-owned program. Many manufacturers have a certified pre-owned (CPO) program, and each one is set up differently. Read on...
Ten Sports Cars That Double as Good Daily Drivers
The best daily driver is a car that's reliable, usable, and still fun to drive. Popular daily sports cars include the BMW M3, Subaru WRX, and VW GTI.