# 2001 Sentra SE won't start



## blackstallion (Jan 5, 2021)

Car won't start, looks like there is no spark (I took out the spark plug and tried the old trick of putting the spark plug next to a ground point on the engine and cranked but did not witness a spark).

Some background, the car has 197K miles. It recently developed a bad oil leak on the valve cover gasket AND into the spark plug well from one of the seals....I found a ton of oil in one of the spark plug wells which probably means something was being shorted out when I cranked the engine.

I ran some checks on the distributor and found the following:

1) Power Supply voltage @ pin 8 was 11.8v (battery voltage was 12.2V)
2) Ignition primary coil resistance taken between pin 7 & 8 was 0.7ohms @ 68F (spec is 0.8ohms) 
3) Ignition secondary coil resistance taken between pin 7 and terminal 9 was 15.5k (spec is 16k)
4) Power Transistor resistance taken between pin 2 and coil pin 8 was 735k (spec says it should be anything but 0ohms)
5) Cap resistor was 670k (spec is 4k-8k)

As far as I can see, everything checked out except #5 for the cap resistor, which I swapped out along with the rotor and plugs. Still won't spark or fire up.

Where else should I be looking to determine WHY I'm not getting spark? 

Is it possible the coils or power transistor in the distributor ARE in fact bad (even though it seems like the measurements I took are basically in line with the specs)?


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## steveX (Dec 20, 2019)

Did you check fuse and ECU relay. ?


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## blackstallion (Jan 5, 2021)

steveX said:


> Did you check fuse and ECU relay. ?


Which fuse? And no I have not checked the ECU relay.


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## VStar650CL (Nov 12, 2020)

If you have supply voltage at the distributor then the ECM fuse and relay are working, the relay supplies the coils as well as the ECM. It does have two separate throws for the ECM supply and the coil supply, so it's remotely possible that the ECM throw is bad but the coil throw is good, but it isn't your most likely culprit.

Do you have a solid security light lit on the dash? _If so, quit cranking it immediately_. A solid lamp means your car has an NVIS system and the IMMU is either dead or rejecting your key. The ECM will basically destroy itself if you continue trying to crank. Either the key or IMMU is bad, so try having a new key programmed first (because that's cheapest), if it won't program then chances are the IMMU (and maybe the ECM as well) is dead. If you replace the IMMU and the ECM still has a "lockout" DTC that won't clear, then the ECM has committed suicide and will have to be replaced.

If there's no security light in the car, or it's there but isn't lit, put a voltmeter on the WHT/BLU wire on pin 4 of the distributor. You should see around 2.5V when cranking, if not then the cam sensor isn't working (the opto wheel inside the distributor). If you find good voltage there, check voltage on the RED/GRN wire on pin 1. That's the trigger from the ECM, and it should go to a non-0 voltage when cranking (probably less than 1V, but above 0). That's the trigger for the power transistor, so if the ECM is trying to drive it but there's no spark, chances are the transistor is dead. Hope this helps you.


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## rogoman (Dec 16, 2004)

blackstallion said:


> I ran some checks on the distributor and found the following:
> 
> 1) Power Supply voltage @ pin 8 was 11.8v (battery voltage was 12.2V)
> 2) Ignition primary coil resistance taken between pin 7 & 8 was 0.7ohms @ 68F (spec is 0.8ohms)
> ...


Since you spoke about the distributor, I'll assume the engine is an SR20DE which has the camshaft position sensor inside the distributor utilizing an LED and the photo diode. The sensor assembly is not replaceable so the entire distributor needs to be replaced. Before condemning the sensor, perform an ECU code readout to see if any DTCs are set; you may be getting a P0340 code which can be caused by any of the following:

- Harness or connectors. The camshaft position sensor circuit is open or shorted.
- Camshaft position sensor itself is bad.
- Weak battery.
- Bad ECU relay.
- Possible bad ECU.
- Bad engine ground connections. Make sure they are tight and clean.


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## blackstallion (Jan 5, 2021)

VStar650CL said:


> If you have supply voltage at the distributor then the ECM fuse and relay are working, the relay supplies the coils as well as the ECM. It does have two separate throws for the ECM supply and the coil supply, so it's remotely possible that the ECM throw is bad but the coil throw is good, but it isn't your most likely culprit.
> 
> Do you have a solid security light lit on the dash? _If so, quit cranking it immediately_. A solid lamp means your car has an NVIS system and the IMMU is either dead or rejecting your key. The ECM will basically destroy itself if you continue trying to crank. Either the key or IMMU is bad, so try having a new key programmed first (because that's cheapest), if it won't program then chances are the IMMU (and maybe the ECM as well) is dead. If you replace the IMMU and the ECM still has a "lockout" DTC that won't clear, then the ECM has committed suicide and will have to be replaced.
> 
> If there's no security light in the car, or it's there but isn't lit, put a voltmeter on the WHT/BLU wire on pin 4 of the distributor. You should see around 2.5V when cranking, if not then the cam sensor isn't working (the opto wheel inside the distributor). If you find good voltage there, check voltage on the RED/GRN wire on pin 1. That's the trigger from the ECM, and it should go to a non-0 voltage when cranking (probably less than 1V, but above 0). That's the trigger for the power transistor, so if the ECM is trying to drive it but there's no spark, chances are the transistor is dead. Hope this helps you.


When would it be concerning for the security light to be solid, even when the car is locked with the key fob? My light is solid, but only in this case, when the car is locked with the key fob.


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## VStar650CL (Nov 12, 2020)

It's only concerning if it's lit solid with the key on. If it goes out when you turn the key, then it shouldn't be a security problem.


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## blackstallion (Jan 5, 2021)

VStar650CL said:


> It's only concerning if it's lit solid with the key on. If it goes out when you turn the key, then it shouldn't be a security problem.


Thanks.

My focus is on WHAT electronics could have been fried (or even fuse's) when the spark plug well was filled with oil (and seemingly shorting out the wire/plug to ground) and I was cranking the engine?

I have no reason to believe the IMMU or ECU is bad since this no start issue started right after the spark plug well was filled with oil.


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## VStar650CL (Nov 12, 2020)

A filled well will usually cause a misfire because it will soften the plug boot and allow the spark to arc through the wire, but it can't cause any other electrical damage. If there are blown fuses or other circuit problems, they won't be due to the well.


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## blackstallion (Jan 5, 2021)

VStar650CL said:


> A filled well will usually cause a misfire because it will soften the plug boot and allow the spark to arc through the wire, but it can't cause any other electrical damage. If there are blown fuses or other circuit problems, they won't be due to the well.


You don't believe something in the distributor ie. coils, high power switch, etc. could be impacted?

Sent from my SM-G965U using Tapatalk


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## VStar650CL (Nov 12, 2020)

blackstallion said:


> You don't believe something in the distributor ie. coils, high power switch, etc. could be impacted?


Only if the burn-through caused the plug wire to go open, then it could overheat the coil primary and eventually kill it. Coils in general don't like to discharge open, the waste energy has noplace to dissipate. Nothing north of the coil primary should be affected.


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## blackstallion (Jan 5, 2021)

rogoman said:


> Since you spoke about the distributor, I'll assume the engine is an SR20DE which has the camshaft position sensor inside the distributor utilizing an LED and the photo diode. The sensor assembly is not replaceable so the entire distributor needs to be replaced. Before condemning the sensor, perform an ECU code readout to see if any DTCs are set; you may be getting a P0340 code which can be caused by any of the following:
> 
> - Harness or connectors. The camshaft position sensor circuit is open or shorted.
> - Camshaft position sensor itself is bad.
> ...


Yes, it's a 2001 SE, so the SR20DE. 

How do I go about getting the ECU code's? I don't have a scanner. I don't want to spend a ton of $ on a scanner either, so looking for any cheaper options or work arounds if they exist.


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## blackstallion (Jan 5, 2021)

VStar650CL said:


> Only if the burn-through caused the plug wire to go open, then it could overheat the coil primary and eventually kill it. Coils in general don't like to discharge open, the waste energy has noplace to dissipate. Nothing north of the coil primary should be affected.


In the original post, #2 documented the resistance of the primary coil at 0.7ohms (spec is 0.8ohms)...I assumed this meant the primary coil was still ok, is this a bad assumption?


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## VStar650CL (Nov 12, 2020)

blackstallion said:


> In the original post, #2 documented the resistance of the primary coil at 0.7ohms (spec is 0.8ohms)...I assumed this meant the primary coil was still ok, is this a bad assumption?


No, 0.7 ohms is fine. I didn't imply that it _would_ kill the coil, only that it _could_ if an open circuit was allowed to persist. A short circuit to the wall of the well, which is what normally occurs with a burn-through, won't harm the coil in the slightest.


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## smj999smj (Jan 1, 2006)

blackstallion said:


> Yes, it's a 2001 SE, so the SR20DE.
> 
> How do I go about getting the ECU code's? I don't have a scanner. I don't want to spend a ton of $ on a scanner either, so looking for any cheaper options or work arounds if they exist.


You can get a low cost, OBD II code reader from any auto parts store or at Walmart in the automotive section for around $25-35. Keep it in the glove and box and it can come in handy as it'll work on US passenger vehicles going back to 1996.


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## blackstallion (Jan 5, 2021)

smj999smj said:


> You can get a low cost, OBD II code reader from any auto parts store or at Walmart in the automotive section for around $25-35. Keep it in the glove and box and it can come in handy as it'll work on US passenger vehicles going back to 1996.


Read the codes:

P1610: ECU locked
P1612: ECU-IMMU chain issue

Using the FCM from another forum and following the troubleshooting procedure, I was able to verify Pins 7 & 8 of the IMMU connector had battery Voltage and Pin 4 grounded as expected.

Next step in the procedure is to check the harness between the ECU and IMMU, which I have not done, but I'm not hanging my hat on the harness being the issue.

The last step, which requires the Consult-2 module to verify the IMMU waveform I won't be able to perform since I don't have the tool, but depending on the outcome of that step, Nissan recommends replacement of either the IMMU or ECU, depending on whether the waveform is present.

I also noticed that the security light on the dash, when the alarm is activated via the FOB, blinks every 30s and stays on for 2s. This does not match any case that the FSM outlines.


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## VStar650CL (Nov 12, 2020)

blackstallion said:


> I also noticed that the security light on the dash, when the alarm is activated via the FOB, blinks every 30s and stays on for 2s. This does not match any case that the FSM outlines.


Yep, that's odd behavior, but it wouldn't be the first error of that sort in a Nissan ESM. What matters is whether the light is on solid with the key in the ignition position. If it is, you either have a dead key or a dead IMMU. Dead IMMU's are common on older Sentras, but try your spare key first before condemning it. Dead keys usually throw a different code (chain of key to IMMU), but that's _usually_. I've seen P1612's from keys that are corrupt but not dead.

It's also possible your ECM has committed _hara kiri_ if it's been cranked too much with a P1610. You generally get 7 tries before a P1610 sets and then another 7 before the ECM commits suicide. So if it isn't dead already, make sure you attempt a code-erase every so often to reset the tries-counter while you work on it. Once you resolve the P1612, if the P1610 won't clear then your ECM is trashed.


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## blackstallion (Jan 5, 2021)

VStar650CL said:


> Yep, that's odd behavior, but it wouldn't be the first error of that sort in a Nissan ESM. What matters is whether the light is on solid with the key in the ignition position. If it is, you either have a dead key or a dead IMMU. Dead IMMU's are common on older Sentras, but try your spare key first before condemning it. Dead keys usually throw a different code (chain of key to IMMU), but that's _usually_. I've seen P1612's from keys that are corrupt but not dead.
> 
> It's also possible your ECM has committed _hara kiri_ if it's been cranked too much with a P1610. You generally get 7 tries before a P1610 sets and then another 7 before the ECM commits suicide. So if it isn't dead already, make sure you attempt a code-erase every so often to reset the tries-counter while you work on it. Once you resolve the P1612, if the P1610 won't clear then your ECM is trashed.


The security light is solid after the key is in the ignition for 5s.

Also, I tried resetting the codes with the OBD scanner and only the P1612 clears, but comes right back after the ignition power is cycled.

Also tried cycling the ignition power 3 times for 5s, did not work.

Also, I've tried these with both keys I received with the vehicle.


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## VStar650CL (Nov 12, 2020)

Well, don't keep cranking it and risk blowing your ECM. Needs an IMMU. The lockout code won't clear until the P1612 is resolved, but by attempting to clear the codes you do reset the ECM's "self-destruct" counter.


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## blackstallion (Jan 5, 2021)

VStar650CL said:


> Well, don't keep cranking it and risk blowing your ECM. Needs an IMMU. The lockout code won't clear until the P1612 is resolved, but by attempting to clear the codes you do reset the ECM's "self-destruct" counter.


Just curious as to why the ECU would blow, is this per design? I don't see anywhere in the FSM that the ECU will blow after a certain number of attempts to start without correct key.

Honestly, in the past several months, as I've attempted to troubleshoot the problem, I'm sure I've cranked it quite a bit, so IF it's part of the design (for the ECU to blow) I'm guessing it would be fried already. Is there an independent way to verify if the ECU is still good or toast?

Also, assuming the IMMU needs to be replaced, I've heard there are ways to rewire and bypass the IMMU and allow the vehicle to start. Can anyone direct me towards a schematic or plan that shows me what needs to be rewired?

This vehicle is really on its last leg and spending hundreds of dollars to replace the IMMU and then bring to Nissan to program would not be worth it.


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## VStar650CL (Nov 12, 2020)

blackstallion said:


> Just curious as to why the ECU would blow, is this per design? I don't see anywhere in the FSM that the ECU will blow after a certain number of attempts to start without correct key.


You won't find it in the SM, first because it's a "Hitachi thing" and you'd have to ask a Hitachi programmer, and second because all Nissan SM's are deliberately vague about the inner workings of NATS or NVIS. But trust me, we replace plenty of them for unerasable P1610's.



blackstallion said:


> This vehicle is really on its last leg and spending hundreds of dollars to replace the IMMU and then bring to Nissan to program would not be worth it.


The IMMU doesn't record any data, so reprogramming isn't necessary. It's a dumb key reader, the ECM has all the smartwork. You can get used ones on eBay for as little as $40 and new for $140. The part number for an '01 Sentra should be 28590-C9901. Changing it isn't difficult.



blackstallion said:


> Also, assuming the IMMU needs to be replaced, I've heard there are ways to rewire and bypass the IMMU and allow the vehicle to start.


The only way I know about is to replace the ECM with a steel-key version from the same MY.


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## blackstallion (Jan 5, 2021)

VStar650CL said:


> The IMMU doesn't record any data, so reprogramming isn't necessary. It's a dumb key reader, the ECM has all the smartwork. You can get used ones on eBay for as little as $40 and new for $140. The part number for an '01 Sentra should be 28590-C9901. Changing it isn't difficult.


Received a used IMMU from ebay for $40. Replaced it, and code P1615 came up instead of P1612....and P1610 still persisted.


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## VStar650CL (Nov 12, 2020)

Try getting the key reprogrammed. Generally P1615 is from a weak IMMU or a weak key, but the new IMMU is definitely communicating with the ECM. Refreshing the smartwork will usually clear it up, although if the issue is a weak key it may come back at some point. If it doesn't clear up after a refresh then that used IMMU has a bad antenna.


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## blackstallion (Jan 5, 2021)

VStar650CL said:


> Try getting the key reprogrammed. Generally P1615 is from a weak IMMU or a weak key, but the new IMMU is definitely communicating with the ECM. Refreshing the smartwork will usually clear it up, although if the issue is a weak key it may come back at some point. If it doesn't clear up after a refresh then that used IMMU has a bad antenna.


I have 2 keys, both are throwing the same code. Programming the key would require getting the vehicle to a Nissan dealer I assume? If so, the vehicle is not worth it and I would probably just get rid of it.

What do you mean by refreshing the smartwork?


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## VStar650CL (Nov 12, 2020)

blackstallion said:


> I have 2 keys, both are throwing the same code. Programming the key would require getting the vehicle to a Nissan dealer I assume? If so, the vehicle is not worth it and I would probably just get rid of it.
> 
> What do you mean by refreshing the smartwork?


On older stuff any locksmith can repro the keys for you, the codes are generic. It doesn't require access to the Nissan database, just having the right software. Reprogramming the keys "refreshes" the memories and handshaking of everything in the NVIS system.


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## blackstallion (Jan 5, 2021)

VStar650CL said:


> On older stuff any locksmith can repro the keys for you, the codes are generic. It doesn't require access to the Nissan database, just having the right software. Reprogramming the keys "refreshes" the memories and handshaking of everything in the NVIS system.


According to the FSM, the key codes or ID #s must be registered into the IMMU and ECM.

So that makes sense now why, when I installed the used IMMU I purchased on eBay, I'm getting P1615 "difference of key" fault code.

Would a locksmith be able to program both the IMMU and ECM as described by the FSM?


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## VStar650CL (Nov 12, 2020)

blackstallion said:


> Would a locksmith be able to program both the IMMU and ECM as described by the FSM?


Yep, it's all part of the same procedure. As I said, entry codes are generic on the older ones, so any smithy with NATS/NVIS software should be able to do it.


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## blackstallion (Jan 5, 2021)

VStar650CL said:


> Yep, it's all part of the same procedure. As I said, entry codes are generic on the older ones, so any smithy with NATS/NVIS software should be able to do it.


It just occurred to me...when I install the replacement IMMU, I get the new P1615 code (difference of key), BUT, with the original IMMU, it's not giving this code. 

Wouldn't this indicate that the key codes are ALREADY good and matching in the original IMMU?


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## VStar650CL (Nov 12, 2020)

Or that the original IMMU isn't communicating. A P1615 is healthy, it means the IMMU is talking but the key needs to be programmed. P1612 isn't healthy, it almost always means a dead IMMU.


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## rogoman (Dec 16, 2004)

blackstallion said:


> Yes, it's a 2001 SE, so the SR20DE.
> 
> How do I go about getting the ECU code's? I don't have a scanner. I don't want to spend a ton of $ on a scanner either, so looking for any cheaper options or work arounds if they exist.


You're dealing with late model vehicles which have a lot of electronics. Getting ECU codes or what's called DTCs *(*Diagnostic Trouble Codes) is vital for diagnostic trouble shooting. Many of the modules are smart devices so if they see a problem, they'll set a DTC. Portable scan tools are not expensive and they can be used on most makes of vehicles. Here are some:



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## blackstallion (Jan 5, 2021)

rogoman said:


> You're dealing with late model vehicles which have a lot of electronics. Getting ECU codes or what's called DTCs *(*Diagnostic Trouble Codes) is vital for diagnostic trouble shooting. Many of the modules are smart devices so if they see a problem, they'll set a DTC. Portable scan tools are not expensive and they can be used on most makes of vehicles. Here are some:
> 
> 
> 
> ...


If you read the thread, you'll see I did purchase a scanner and learned what codes were present.


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## blackstallion (Jan 5, 2021)

VStar650CL said:


> Or that the original IMMU isn't communicating. A P1615 is healthy, it means the IMMU is talking but the key needs to be programmed. P1612 isn't healthy, it almost always means a dead IMMU.


Got a quote to reprogram for $120! Honestly don't believe it's worth trying, as I'm still thinking there's a good chance the ECM could be dead as well.

At this point, it seems I have exhausted my options with this vehicle.

Wondering what my best option would be at this point, considering getting rid of it as well...


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## VStar650CL (Nov 12, 2020)

Even if the ECM committed hara kiri, there are plenty of good used ones on eBay in the $100~150 range. Chances are it's fine, the P1615 just means the new IMMU works and now it needs a key program. You can make it more complicated than that, but it probably isn't. The $120 for programming is a little piratical. Our shop charges half an hour for steel-key repros, which is a bit more than half that amount.


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## blackstallion (Jan 5, 2021)

VStar650CL said:


> Even if the ECM committed hara kiri, there are plenty of good used ones on eBay in the $100~150 range. Chances are it's fine, the P1615 just means the new IMMU works and now it needs a key program. You can make it more complicated than that, but it probably isn't. The $120 for programming is a little piratical. Our shop charges half an hour for steel-key repros, which is a bit more than half that amount.


What would be involved in the steel key conversion? What does it typically cost in parts and where do I source them?


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## VStar650CL (Nov 12, 2020)

Probably just an ECM repro, but I'm not sure how you'd go about finding the right firmware p/n other than to find a used ECM from a steel key model.


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