Car trouble.

"Rainbow" (rainbeaux) 01/18/2019 at 14:34 • Filed to: None

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I hit a speed bump at like 15mph and my engine cut off. It came back on after a few seconds of starting, but now I have a CEL and my tach doesn’t work. Does anyone know what could be causing this before I walk all the way to Walmart for a code reader?

Update: tach is back, but still CEL.

Update 2: CEL is off. I decided to drive the car to Walmart to see if it felt any different, and upon leaving the store, the light was off. They were out of scanners anyway, so I’ll get one later.

E90M3 > Rainbow 01/18/2019 at 14:40

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Have you tried reversing over the same speed bump at 15 MPH? 

Aremmes > Rainbow 01/18/2019 at 14:45

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Probably so me ignition harness got loose and cut the signal to the tach.

facw > Rainbow 01/18/2019 at 14:46

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Sorry no. I highly recommend spending the $10-15 for a cheap Bluetooth code reader though.

razorbeamteam > Rainbow 01/18/2019 at 14:55

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My tach is linked to my alternator and I know that’s the same on a lot of other cars. I would start there. 

HFV has no HFV. But somehow has 2 motorcycles > Rainbow 01/18/2019 at 15:03

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cam angle sensor/ crank sensor with a bad connector ? maybe it jiggled on the bump, the ECU stored that code so its still giving you a CEL.

Full of the sound of the Gran Fury, signifying nothing. > Rainbow 01/18/2019 at 15:43

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Check battery terminals first. I’ve had some very weird things happen to the Mazda5 when I went over a bump after I forgot to tighten up the ground cable.  CELs, random electronic things not working, lots of bizarre warning lights. All went away after tightening that cable. 

Die-Trying > Rainbow 01/18/2019 at 15:49

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i would check the battery terminal connections first thing.......

gogmorgo - rowing gears in a Grand Cherokee > Rainbow 01/18/2019 at 16:55

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Don’t remember what you drive.

Battery cables don’t usually kill engines that are already running, but bad connection to both battery and alternator could I suppose. Worth checking... you never know on modern cars. On a similar note, make sure the engine block is properly grounded to the body, I’ve seen the chintzy braided ground strap fatigue or corrode and break and cause similar problems. The engine doesn’t always  ground so well through the rubber mounts.

If you’ve got a HEI coil and distributor à la ‘80's and ‘90's, (or older, TBH, but no CEL) that’s typically where the tach gets its signal, and a loose connection to coil power will kill an engine. Crank position sensor connections also can do similar things on more modern applications.

Also make sure the ECU connection is tight and all pins are clean. Usually they’re bolted together to prevent wiggling loose and it’s not uncommon for them to get plugged back in without the bolt being tightened. CEL should come on if the ECU is unplugged, but wouldn’t usually store a code.