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Error Code 21 On Bnr34

Alecci

By Alecci,
in General Maintenance

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Alecci Apprentice

Alecci

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I've been rebuilding my R34 GTR following a crash during a track event some two years ago.

I've modified most of the engine, basically only leaving the bottom end standard.

For a complete spec list, please visit this link and scroll down below the pictures. All parts used are brand new.

For some time now we've been trying to start the car. We've run diagnostics on it and gotten some error codes, and we've managed to sort them all out except for code 21 (primary ignition signal).

I've searched the forums for other threads describing the same problem, and while the search turned up a lot of results for error code 21, none of the threads has dealt with problems such as mine (i.e. the car will not start at all).

We have spark on all cylinders, and we have fuel going into the engine. Ignition angle is 16 degrees. The starter turns over quickly and the car sounds like it wants to start, but the closest thing to a running engine we've achieved is a lot of back-firing in the exhaust.

I'm a real newbie when it comes to troubleshooting cars and fixing problems, but my guess is that one of the following are broken or not functioning properly:

- cam-angle sensor

- coilpacks

- AFM's

Any thoughts? I've posted this question on a number of other forums, but I don't seem to get any help. Having spent the last 2 years rebuilding the car, whereof the last 2 months just trying to get it started, I'm close to losing heart and taking a sledgehammer to the car in order to smash it just for the sheer satisfaction of the act. Help is desperatly needed!

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GeeTR Grand Master

GeeTR

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I checked the link, nice setup man, looks smooth :blink:

If its complaining about the primary ignition signal, Id assume that to mean the CAS isn't behaving correctly. I'm not too familiar with RB26 CAS's, but id assume its a photodiode and chopper disk setup. 360 (=20) home slots and 6 trigger slots. If "Primary Ignition Signal" isnt refering to the whole CAS, maybe just one of those ouputs is broken, as i didnt think a RB would even fire without a CAS. I guess the obvious question is, have you tried a different CAS?

I'm just just thinking aloud here :(

GoodLuck

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Alecci Apprentice

Alecci

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I checked the link, nice setup man, looks smooth :(

If its complaining about the primary ignition signal, Id assume that to mean the CAS isn't behaving correctly. I'm not too familiar with RB26 CAS's, but id assume its a photodiode and chopper disk setup. 360 (=20) home slots and 6 trigger slots. If "Primary Ignition Signal" isnt refering to the whole CAS, maybe just one of those ouputs is broken, as i didnt think a RB would even fire without a CAS. I guess the obvious question is, have you tried a different CAS?

I'm just just thinking aloud here :D

GoodLuck

Hi mate,

I don't have any clue whatsoever as to how the CAS is constructed, nor in which ways it could be broken to the point where the car will not start.

I've not had nor will have any chance of trying a different CAS. There's only about 12 BNR34's in Sweden altogether, and none of them are close to where I live. Being a delicate, rather expensive and crucial component of the engine there's no way I can borrow one either.

The same thing, of course, goes for the coilpacks.

Being a bit low on funds after spending some money on the rebuild of the car, I'd hate buying new stuff that's not really needed.

Many thanks for your reply, I really appreciate it.

Cheers!

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blind_elk Grand Master

blind_elk

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Error codes in Nissan ECUs are persistent, ie they "hang around" for something like 50 start cycles. Try clearing (resetting) the ECU, see if you still have the error code.

If you have spark, then the CAS is working correctly. That also rules out the coil packs. And most engines will start without an AFM.

Do you have fuel "going into the engine" because you have fuel at the rail, or because you have seen the injectors working?

Are you sure the cams are set correctly? You had the crank at TDC when you assembled the cambelt?

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Alecci Apprentice

Alecci

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Error codes in Nissan ECUs are persistent, ie they "hang around" for something like 50 start cycles. Try clearing (resetting) the ECU, see if you still have the error code.

If you have spark, then the CAS is working correctly. That also rules out the coil packs. And most engines will start without an AFM.

Do you have fuel "going into the engine" because you have fuel at the rail, or because you have seen the injectors working?

Are you sure the cams are set correctly? You had the crank at TDC when you assembled the cambelt?

Diagnostics tool and ECU has been reset/cleared between starts. We also removed the cable to the CAS, and then we would only get error code 11 (cam angle sensor). When CAS was reconnected, we once again only get error code 21.

Fuel is going into the cylinders, the spark plugs got very wet prior to lowering the fuel pressure. The injectors still open 8.0 ms when cranking the engine, some people guess the reason for that is choke (fuel enrichment for cold starts). Fuel is still going into the cylinders after lowering the fuel pressure. If I'm not mistaken, the car would not be back-firing if there's no fuel present?

Crank was at TDC and we double, triple and quadruple checked the position of the cams prior to assembing the cambelt.

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GeeTR Grand Master

GeeTR

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The fact its spitting code 11 when the CAS isn't present, and a 21 when it is... I got my money on the CAS. Have you got access to a oscilloscope to check its output maybe? Could the loom be damaged between CAS and ECU?

Edited by GeeTR
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Alecci Apprentice

Alecci

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The fact its spitting code 11 when the CAS isn't present, and a 21 when it is... I got my money on the CAS. Have you got access to a oscilloscope to check its output maybe? Could the loom be damaged between CAS and ECU?

Just like you said, the fact that a non-present CAS gives code 11 and a present one gives code 21 is what also made me suspect that it may be the CAS that's malfunctioning. Otherwise I think the first error code would still show up, right?

The wiring could be damaged I guess, but it's nothing that meets the eye at least.

I'll check access to an oscilloscope.

I'm very grateful for your input!

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Alecci Apprentice

Alecci

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The car finally started this morning. It was the CAS... It probably took a good smacking in the crash (no damages were visible until we opened it up).

Thanks for your assistance, guys!

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