Thread: Motor died - multiple error codes - clueless where to start looking

one coil fires two cylinders. try changing the coolant temp sensor for the p0125 code. o2 sensor shouldnt make the car die. as for the p0300 code, there are multiple things that can make it misfire and i could list them all, but i think ill let the more experiance guys get that one.

pull the plugs, look for damage.

I'm with FFDP on pulling plugs. You wouldn't be looking for a true plug issue, but anything odd with them. Say for example if they were damaged or soaked with coolant. Wet plugs don't fire. Being a non-SC it's possible to have a ruptured UIM soak your motor in coolant. That could cause the coolant sensor to read incorrectly (no coolant = funky air reading off sensor) etc etc.

As well, checking the fuel pump as Nacho said is a great idea too. I'd probably add in pushing the schrader with a rag to see if fuel spurts out. Only because I've heard a pump actuate w/o pumping enough pressure to start an engine. It's uncommon....but hey.. I wonder at times...if everything hasn't happened to me.

UIM is upper intake manifold, the black thing right under the fuel rail.
Schrader is the tire fill looking valve on the fuel rail up front. When you push down on it..you should get a good spurt of fuel (instead of air).

for research look up lower intake gasket replacement. that will give you all you need to get down and find any coolant leaks in the intake system.

as for figureing out if you have an intake leak. Like said, pull the plugs and look there. I would also look to see if your coolant is low at all... check in the radiator too if it if very low you could have a leak in the intake as the coolant had to go somewhere.


if it doesnt start i would go from ground zero and start from scratch.
1) Pull plugs check for coolant like said, if they look lean or rich, any damage, then a compression check if the plugs look fine. If good on to next step
2) Fuel pressure check at rail. if you can find one to rent an injector test light. but a fault in the wiring is rare.
3) Spark as long as one wire from each coil pack throws a spark from the terminal to the wire both will be good 9/10 cause its a loop system.

all you need is air fuel spark and it will fire. if your close to stock you can pull the battery to reset the fuel trims on the PCM and then disconnect the MAF and start it. will go into limp/ open loop mode. its all about ruling out variables.

when my DOHC jump time i pretty much had to run thru the big three scratching my head cause everything looked fine on the fuel and spark section. the DOHC is AL head so i didnt want to pull the plugs and strip them. also i was without my compression tester anyway. a compression check would have told me imediatly that i had a problem. later when i tore it all down i had air blowing out the intake side of the heads!