Can an ECU go bad in parts?

[MattInARedMicra]

update in post 12





The question is: Can an ECU go bad in parts?

The mileage is still displayed on the dash, the fuel gauge displays correctly, the car still turns over, there is a noise from the fuel pump when you turn the key to accessory showing that it's primed, nothing flashes on the dash when turning the key for the immobiliser, there's no water on it or it's dried if there was the last time it ran, the engine warning light is illuminated when turned to accessory and turns off while turning the engine over, it comes back on when you let it sit on accessory... all those which makes me think ECU is fine

But there is a consistent "link error" when connecting an OBD11 even with the radio fuse removed which I'm told sometimes affects the OBD. Bridgeing the two pins on the data terminal doesn't flash the engine warning light on the dash to read the error code that way (I have bridged the same 2 connections in the past a few years ago and got it to flash on the dash so this is recent), the thing will not start although it turns over and sounds like it wants to go. It never had any intermittent problems in the past, it just cut out one time while driving and never started again. There was a blown fuse in what the sticker on the panel cover called "ignition signal" and what the haynes manual called "engine control unit". All those things make me think the ECU is toast.


It's 1999 k11 1.0l facelift, which I think is either NATS 2 or NATS 5 (red chip in the key). It has a distributor not coil packs. no other fuses or relays are broken. Battery has been recharged outside the car a bunch and when it got towed I was told battery is fine under load test. I also did try a little fuel on the air filter which was probably a bad idea, nothing happened which should supposedly rule out a fuel problem if it had started for a couple seconds but perhaps I did it wrong or it's a bad test

any ideas? hope you're all having a good Easter

 

[MattInARedMicra]

A quick update, I ordered an ECU anyway, I'm going to plug it in on Sunday, get the battery fully charged, put in back the car, and sit there pleading with whichever god is most forgiving that it starts on the button when I turn the key

If it doesn't start then I'm flat out of ideas as to what it could be, and it'll probably be the end of the Micra. I said I'd drive this car into the ground but I really hoped it'd be the engine failing catastrophically or something exciting at least, not just electrical problems I can't track down or something MOT related now it's been sitting a few months. Wish me luck I guess.

 

[.Maarten]

Could be a nats issue. Another ecu wont solve That because you also need the chip from the key And ring around the ignition barrel. If you got all That iT could solve iT But cant be sure without a proper diagnoses. Does the led in the dash stop blinking Or does iT light up solid? Or does iT Go off If you start the car?

 

[MattInARedMicra]

Could be a nats issue. Another ecu wont solve That because you also need the chip from the key And ring around the ignition barrel. If you got all That iT could solve iT But cant be sure without a proper diagnoses. Does the led in the dash stop blinking Or does iT light up solid? Or does iT Go off If you start the car?

The lights all come on solid when turned to accessory, the car won't start and the engine warning light (yellow) goes out while attempting to start but then comes back on solid when it's back to accessory.

I've found conflicting information everywhere about NATS, some say it cuts ignition spark allowing the engine to turn but not start, others saying it cuts the fuel pump, some say it will start only for a few seconds, some saying you won't be able to turn it over at all because the starter motor won't run. I'm not very good at reading electronics diagrams and having difficulty figuring out if the problems are caused by the components or by an attempt to stop me stealing my own car or a dodgy ecu.

I've got one coming with a new key and transponder ring so hopefully I can rule it out if nothing else. Will be a fairly expensive way to find out it's broken beyond repair though

 

[frank]

nats cuts the injector signals matt, so if it runs for a few secs when you drop some fuel down the throttlebody, then that indicates a fuel or nats problem

 

[plmval]

No Spark ?

Quote; “consistent "link error" when connecting an OBD11” ?

1999 K11 is OBD1, test socket has 14 pins out.

OBD 11 test socket has 16 pins out & not interchangeable.

Ignition fuse failure that you refer to is more likely to have been caused by distributor/HT coil failure rather than very rare ECU failure.

Check that the distributor is turning?

Reinstate oem parts & initiate logical fault inspection test sequence instead of replacing parts.

Multimeter testing of 12 V power at distributor, injectors & ECU as per Haynes circuit diagram.

Use back probe T Pins to access the back of connectors live in situ when circuits are powered up & or operating. ( I use paper clips or sewing pins to puncture thru wires or whatever is to hand )

Ref;

If 12V present everywhere that its rqd, then distributor failure is not uncommon if no spark present when starting.

Good luck

 

[MattInARedMicra]

No Spark ?

OBD 11 test socket has 16 pins out & not interchangeable.

I bought the wrong one and then bought a 14-16 pin converter for it, I was told it was backwards compatible

Ignition fuse failure that you refer to is more likely to have been caused by distributor/HT coil failure rather than very rare ECU failure.

The distributor has failed and then been replaced in the past, the first time it went it didn't take a fuse with it but I never did figure out what killed it. On that instance it had ran fine the last time I'd used it and then just wouldn't start one morning. I just fit a new one and it started working again that time. This time though - I didn't think it was possible for a distributor to cause a "failure in flight" because it wasn't running rough or causing any problems with acceleration the night it stopped running. I would have thought that a weak spark or misfire/mistiming/a cylinder down or something like that would come before a total failure

Multimeter testing of 12 V power at distributor, injectors & ECU as per Haynes circuit diagram.

Use back probe T Pins to access the back of connectors live in situ when circuits are powered up & or operating. ( I use paper clips or sewing pins to puncture thru wires or whatever is to hand )

If 12V present everywhere that its rqd, then distributor failure is not uncommon if no spark present when starting.

Sorry what is "rgd" ? ... Now that I know this I can try to test. The fuse has been replaced and has not blown during subsequent starting attempts so every part you mentioned should be getting 12 volts is that correct? The ECU already arrived but I'm having trouble getting it out of it's bracket and the new one came without a bracket for some reason so it's not currently able to be mounted in the car anyway. I can put the old one back in and give this a try. Thank you for the long post too mate, very helpful

 

[MattInARedMicra]

nats cuts the injector signals matt, so if it runs for a few secs when you drop some fuel down the throttlebody, then that indicates a fuel or nats problem

That makes sense. I know all these anti-theft systems were useful once upon a time when car theft didn't just involve nicking somebody's keys but my god it doesn't half cause a headache now trying to figure out if something is broken or if the ECU is intentionally breaking something to try to foil this non-existent theft attempt on my precious Micra

do you know do k11 micra (1999) flash anything on the dashboard if NATS is interfering because this would solve a big diagnostic issue?

 

[.Maarten]

The led near the heater is for nats. If iT flashes iT doesnt see a chip/key. If you insert the key iT should Go off.

 

[plmval]

Rqd = Required

Key code recognition issues or a Nats failure result in the Nats antitheft system interrupting the injectors firing signal only. Thus it turns over but will not start as no fuel. Have you tried spare keys?

Once my earlier 96 K11 would not initially start & the CEL was flashing only while trying to start but it would not start. Removing the key & trying again & CEL did not flash & it started & never repeated this snag again.

Franks test adding fuel down the TB & still not firing indicates no spark/possibly distributor fault or it not turning/cam chain fault & or a lack of any of the 12V power supplies earlier referred too.

Changing ECU due to failure is last on the list & codes may not be compatible with EPS, ABS & instrument binnacle display.

What work or mods have recently been done to the engine or electrics wiring anywhere, if any?

 

[MattInARedMicra]

The led near the heater is for nats. If iT flashes iT doesnt see a chip/key. If you insert the key iT should Go off.

Rqd = Required

Key code recognition issues or a Nats failure result in the Nats antitheft system interrupting the injectors firing signal only. Thus it turns over but will not start as no fuel. Have you tried spare keys?

Once my earlier 96 K11 would not initially start & the CEL was flashing only while trying to start but it would not start. Removing the key & trying again & CEL did not flash & it started & never repeated this snag again.

Franks test adding fuel down the TB & still not firing indicates no spark/possibly distributor fault or it not turning/cam chain fault & or a lack of any of the 12V power supplies earlier referred too.

Changing ECU due to failure is last on the list & codes may not be compatible with EPS, ABS & instrument binnacle display.

What work or mods have recently been done to the engine or electrics wiring anywhere, if any?

The only mods that were ever done was changing out the radio it came with and no problems were ever caused by that, I did remove the fuse for it just to make sure that wasn't causing the link error because youtube said it could (although that was in a VW). Some issues with brakes, one distributor replaced, bit of welding, one time it flooded and I did the fuel pump fuse trick so I know how to catch that one, but other other than that it's been absolute gold. It'll be such a shame if I can't fix this. Still only got 45,000 on the clock and it's taken me some places

I did do the fuel down the throttle body but there's a very good chance I did it wrong, I didn't want to use too much and I didn't have anyone available to turn the key while I was doing it so I just put a little on the airfilter. I did rule out a fuel problem with this or so I thought (the AA driver said it sounded like a fuel issue, and thought my fuel filter was blocked, I've since changed the fuel filter it was the first thing I tried) but at the time I didn't know that the injectors refusing to pulse was a NATS thing I thought that NATS cut the fuel pump . With this knowledge it would make sense to try to repeat this test.

I've never noticed a flashing check engine light, the only time it has ever flashed at me was when I bridged the OBD with a paperclip a few years back and was able to get codes from it. Another thing I didn't know is the location of the light on the ECU, there were a ton of holes in the side of it on both sides and I think I'd already taken the battery out by this point so I never did see if it was flashing because it didn't have a key in or it didn't recognise the key. I'd try another key but I only bought it with one.

I'm still at a bit of a loss, because no injector pulse would meet both the condition of ECU failure, NATS interference, and also what the AA guy said about blocked fuel seeming like the issue when he briefly checked it over that one night at 4am. I'm pretty good with fixing things, but computers/electronics are just way above my head, I thought the wiring diagram was a map of the Tokyo underground at first and if I'm honest that would have probably been more use to me .

The weather is crap at the moment, I wanted to do it this weekend, even more so now I've got this wealth of information of things to try and how to do it, I'm going to try to do some proper diagnostics and do things correctly now probably the start of next week when the sun comes back out. This wind is driving me mad sat inside lol

 

[MattInARedMicra]

Finally had a chance to get out and have another go, got some updates.

ECU fitted to the car, battery fully charged and back in, fuse replaced that had blown, was able to bridge the obd1 connector with a paperclip to get code 55 (nothing wrong). It wasn't entering diagnostic mode like this before, but for now my ECU is sorted. MIL (check engine line) flashes codes again, and the light on the back of the ECU flashes at the same time. The red LED on the dash flashes to say NATS is active, and when key is turned to "ON" it stops flashing. The MIL is not flashing as it would if it was immobilised. No NATS problem that part is solved now. MIL goes off if I attempt to start the car, car still does not start.

had a bit of a play around and took the HT leads off, had some old working spark plugs to plug in and had cylinder 1 and 2 refusing to spark with the sparkplug grounded on the engine. I did measure the resistance in the HT leads. got 3.4kΩ in 1, 3.4kΩ in 2, 2.2kΩ in 3 and 1.2kΩ in 4. The leads closer to the distributor are shorter and so that's a possible reason for the lower resistance so I'm not sure if this shows faulty HT leads or not.

then I put everything back together, pressed them on firmly, checked all the plug and play connectors attached to the distributor/injectors/throttlebody gave it another go at cranking for 10 seconds. Still no start. Tried again to get codes from the paperclip trick. After previously getting 55 (no fault) I'm now getting fault 21 (21: ignition signal circuit) - has it thrown this code because I cranked it with the ht leads disconnected from the plugs?

 

[plmval]

Quote; “has it thrown this code because I cranked it with the ht leads disconnected from the plugs”?

Cranking or turning over the motor with the HT leads disconnected from a plug or the plugs, with ignition circuit live (fuses in), has high risk & may blowi/short the HT coil & its controlling low voltage components.
.
Extra high volts generated with nowhere to go, as HT output is open circuit with any leads disconnected at any time of cranking as you describe & may have induced an ingnition fault.

Should use a spark tester or a single plug at a time always connected and grounded earthed on the engine/head block, at all cranking time operations, & is a two person test.

Reference;

 

[MattInARedMicra]

Quote; “has it thrown this code because I cranked it with the ht leads disconnected from the plugs”?

Cranking or turning over the motor with the HT leads disconnected from a plug or the plugs, with ignition circuit live (fuses in), has high risk & may blowi/short the HT coil & its controlling low voltage components.
.
Extra high volts generated with nowhere to go, as HT output is open circuit with any leads disconnected at any time of cranking as you describe & may have induced an ingnition fault.

Should use a spark tester or a single plug at a time always connected and grounded earthed on the engine/head block, at all cranking time operations, & is a two person test.

Reference; 064Ilsz8Fzg[/MEDIA]
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Yeah that was similar to what I did. I didn't have a proper spark tester (the screw kind where you see if you have a strong enough spark to jump a 30kv gap) nor did I have the lights where you connect the ht lead to a light and ground the light with some jumper cables. I just put a sparkplug in the end of the ht lead and then put the metal part of the sparkplug against the engine so that had it been working the spark should have jumped from the inside of the ceramic across the gap and into ground. Once I realised I had no spark in cylinder 1 and 2 I assumed I probably didn't have spark in any of them. also cylinder 1 and 2 were close enough to the drivers side and the key that I could put my left arm through the window to turn the key and see the sparkplug well enough to check for a spark, would have been a lot easier had I had another person to help out but it's a bad idea to be too close to the ht leads while the ignition system is running anyway like you said, lots of volts involved.

I'm starting to get a clearer picture of what's actually happened to it now. I think that the distributor was probably the original problem, but when it failed it took out fuses and possibly messed something up inside the ECU. Having followed all the fuses/relays and checked them for continuity, replacing the bad one, and trying to bridge the OBD1 connector and maybe doing it wrong the first time I tried I killed the ECU. So rather than having one problem I've had the dizzy, a fuse, the ECU and NATS all at once, which has made the diagnostics that bit more complicated. ECU replaced and fuse replaced has cleared up that problem, and now it looks like the only one left to solve is the spark issue that caused all this in the first place.

I'm a bit miffed because I'd already replaced the whole distributor 3 years (less than 10,000 miles) ago and it's not like I drive it hard or anything, lots of motorway miles driving up to newcastle and back and then just a bit of pottering around town. To get to work I always had a lift in a company vehicle so I wasn't putting daily miles on it really. The car has 46,000 in total.

Not sure what has failed inside the distributor. The first time it took no fuses with it and caused very few problems, I had even less of a clue back then than I do now but looking back I think it was probably the rotor/cap that went that time, being a known issue on micras I just replaced the whole thing with one from a scrappy thinking I was saving myself a headache with towing. Now it looks like possibly the internal windings have gone since it's done so much damage? I'm gonna replace the cap/rotor and hope for the best but if it turns out to still not start after that I'm looking at £145-200 for a brand new distributor from nissan because I can't be arsed messing around with one from a scrapyard and going through this again and again. If it has boobs or wheels it'll give you trouble, said my grandad a long time ago