[truckchick78]

This question came up when working on a Nissan Sentra, but I was told it was true with all Nissan ECU's.

The background is a Sentra has had a starting issue since about 20k miles. It has never turned on the SES until now at 97k. It has always started, but had a rough idle until you give it some gas and then it settles.

Now that the light is on, they are having me look at it. The code is a cylinder 3 misfire. After swapping coils and plugs with another cylinder, it says the same thing. After changing the fuel injector, it runs great, but the light came back on with the same code.

They have now taken the car to a shop. The shop verified that there is no misfire. The mech says that Nissan ECU's are filled with a jelly and after 8-10 years it dries out and the computer can fail. He also says that the injector has been the problem the whole time, but now the computer is bad and turning the light on in error. This car needs to pass an emissions test, obivously it doesn't with the light on.

Has anybody heard of this before? I have had ECU's go bad before and it started throwing all kinds of different codes, not consistanly the same code. I'm not sure if the guy is full of crap or what to do about it.

 

[2WD_NISMO]

Well, I don't know about the "jell" theory and Nissans because the ECU in my 18-year-old Sentra hasn't failed yet.

 

[chaz]

is that grape jelly,sorry never heard of any jelly in the ecu,did it get reset properly after repair?was it disconnected(neg term on batt)during operation.
the ecu unit rarely fails,they are built to last as long as possable.
(i know they can fail)usually they get tampered with ,flashed hyped up with other things.

 

[truckchick78]

I know the codes have been reset several times. The light comes on intermittently. I know when I swapped the coils and reset the light, I still got a pending code for the #3 misfire. Because of the pending code the computer won't finish the test.

I've called them and told them I want to reset the computer by disconnecting the battery and see what happens. This car has had no mods done to it. Is it possible to take it to the dealer and have them flash the ECU?

 

[bwarren228]

Have you done a compression test?

 

[truckchick78]

Compression test and leak test both looked good.

 

[carphreak]

what year is your vehicle? there was a recall on 2000-2003 sentras :
NHTSA CAMPAIGN ID Number: 03V477000
Consequence:
IF ONE OF THE RESISTORS INSIDE THE ECM HAS A CRACK ON THE SURFACE COATING, THE GAS MAY CAUSE CORROSION OF THE RESISTOR. THIS COULD CAUSE THE MALFUNCTION INDICATOR LIGHT TO COME ON, POOR DRIVABILITY (IDLE INSTABILITY, POOR ACCELERATOR), OR THE ENGINE TO STOP RUNNING DURING VEHICLE OPERATION, WHICH COULD RESULT IN A CRASH.

fyi: i didn't type all caps, i just copied and pasted it from the nhtsa website...

 

[truckchick78]

It's a 2003. I'll check into this then. Thanks for the info.

 

[carphreak]

good luck! keep us posted

 

[truckchick78]

The owner called the number listed on the recall and they said that it was not effective for her car. Back to square one I guess.

 

[steve500]

Bad ground on the ignition system will cause sever ECU problems.

Happened to me, bad ground on the engine (small ground wires bolted to the top of the engine ), contact got a little corroded, first was random misfire codes and 2nd, the ECU died. New ECU, fixed the ground and made it more heavy-duty, perfect.

 

[BRUTAL]

^^^ I agree, now I would start looking closely at the pins at the ecu and coil, did you swap plugs too?

 

[truckchick78]

Yeah, I swapped the plugs and the coils. I will be checking grounds for corrosion later today.

 

[BRUTAL]

Not Just Corrosion, But Loose And Or Spread Pins

 

[mrgrayaz]

I just did a coil on a 2000 sentra. Got a Cyl 1 misfire, swapped plugs (they were original @120k),Cyl1 was black, still threw Cyl1 misfire. Swapped coil over to plug 4, cleared the code and got a Cyl4 misfire, replaced the coil and it went away.

Poor idling, and driveability. Sounds like a different problem, but I thought it was funny we were both doing coil swaps on QG18DE's within a week of each other

Throw a couple extra ground wires on to test the engine ground theory. Find a random bolt and crank some wires on there, if it solves your problem, make some nice ground straps and perminately attach.

 

[truckchick78]

For those that wonder, I had the owners bring me the car to look at again. They said they were having intermitent SES light flashes and a couple issues of rough starting. I checked the computer and didn't have any pending codes (I did the last time).

I checked some grounds, cleaned some battery corrosion, etc. Thats when I noticed the coolant overflow bottle was empty. Popped the radiator cap and started it up. It was blowing bubbles in the coolant. So, it's time for a head gasket. At least that mystery is solved.

Thanks for all the advice though!! :urthebest: