993 check engine light mystery solved
Discussion
I've owned my '95 NVR 993 for 12 years, and to be honest, never paid much attention to the warning lights on the dash so long as they all went off on startup. The car had been running really badly for a while with no engine light illuminated, which was eventually diagnosed as the HT leads needing replacing. This was done and I collected the car the other day, and it was massively improved, but still felt a bit rough at low revs, maybe a bit down on power, and maybe a bit fuel hungry. But to be honest I hadn't driven it for more than a few mins in so long, that I could have just been imagining it.
Still, I decided to check for any fault codes. Then I realised I didn't have an OBD1 reader...booo. Then I found out you can read them from the check engine light...yaaay. So, I followed the procedure and kept my beady eye on the "!" light on the dash, but no joy. Went to google....turns out that's not the check engine light as I thought it was....! Also turns out, the actual Check Engine light wasn't even lighting up when switching ignition on. Riiiight, blown bulb then. So I pop out the dial and look at the back aaaaand......the CEL bulb slot had a blank in it rather than a bulb
And yet the ABD slots (the two blue ones to the right of the blank in the picture) which I am 99% my car was not specced with as I have never seen either of them come on and only just discovered actually existed for 993s, had bulbs in
So I pulled one of these, checked it was okay with a multimeter, and swapped it and the CEL blank over. Lo and behold, I now have a check engine light that works!
I could swear I've never seen that light on ever on startup, and if I have, it would have been at least 10 years ago. Only thing I can think of is that when I sent the dials off to be refaced / repaired 10 years ago, when they were checking / swapping bulbs, they put them back in wrong.
Anyway, with the working CEL light, I checked the stored engine codes and got 1221 and 1218. These are to do with MAF and RPM sensor respectively I think based on https://forums.pelicanparts.com/porsche-911-techni... and the 2 digit DTC codes here https://www.troublecodes.net/Porsche/#codesobd1 - I can't seem to match the full 4 digit ones to anything, but MAF definitely makes sense as it felt like the car was running in some sort of "safe" backup map/mode.
Btw, if anyone has a reliable list of fault codes for OBD1 993s, it would be most helpful.
So, I cleared the fault codes and just took the car for a brisk 8 mile run, and she's feeling much better I think. No new codes appeared. Engine now sounds "right" like it used to, throttle is a lot smoother below 3k rpm, feels like she's got a bit more power and I think fuel consumption may have improved as my remaining fuel mileage actually went up during the journey despite me doing the usual route but giving it the beans more.
So happy days, will keep and eye on it and do a few more test drives, but hopefully I now have a better running car AND a mechanism to see when I might have a problem
Still, I decided to check for any fault codes. Then I realised I didn't have an OBD1 reader...booo. Then I found out you can read them from the check engine light...yaaay. So, I followed the procedure and kept my beady eye on the "!" light on the dash, but no joy. Went to google....turns out that's not the check engine light as I thought it was....! Also turns out, the actual Check Engine light wasn't even lighting up when switching ignition on. Riiiight, blown bulb then. So I pop out the dial and look at the back aaaaand......the CEL bulb slot had a blank in it rather than a bulb
And yet the ABD slots (the two blue ones to the right of the blank in the picture) which I am 99% my car was not specced with as I have never seen either of them come on and only just discovered actually existed for 993s, had bulbs in
So I pulled one of these, checked it was okay with a multimeter, and swapped it and the CEL blank over. Lo and behold, I now have a check engine light that works! I could swear I've never seen that light on ever on startup, and if I have, it would have been at least 10 years ago. Only thing I can think of is that when I sent the dials off to be refaced / repaired 10 years ago, when they were checking / swapping bulbs, they put them back in wrong.
Anyway, with the working CEL light, I checked the stored engine codes and got 1221 and 1218. These are to do with MAF and RPM sensor respectively I think based on https://forums.pelicanparts.com/porsche-911-techni... and the 2 digit DTC codes here https://www.troublecodes.net/Porsche/#codesobd1 - I can't seem to match the full 4 digit ones to anything, but MAF definitely makes sense as it felt like the car was running in some sort of "safe" backup map/mode.
Btw, if anyone has a reliable list of fault codes for OBD1 993s, it would be most helpful.
So, I cleared the fault codes and just took the car for a brisk 8 mile run, and she's feeling much better I think. No new codes appeared. Engine now sounds "right" like it used to, throttle is a lot smoother below 3k rpm, feels like she's got a bit more power and I think fuel consumption may have improved as my remaining fuel mileage actually went up during the journey despite me doing the usual route but giving it the beans more.
So happy days, will keep and eye on it and do a few more test drives, but hopefully I now have a better running car AND a mechanism to see when I might have a problem
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