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CEL Mystery?!

Help, Advice and DIY Tutorials on Volvo's extremely popular car line -- Volvo's 1990s "bread and butter" cars -- powered by the ubiquitous and durable Volvo inline 5-cylinder engine.

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smigg21
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CEL Mystery?!

Post by smigg21 » Sat Jan 12, 2008 7:17 pm

Ok, get ready for this one.
My intent on cleaning the pcv system, throttle body, and egr was to obviously enhance the performance and life of the engine. FYI, the CEL has been on since i bought the car 2 years ago('94 turbo 850 2.3l), and always had some "not so serious" codes set (i think MAF or O2 sensor came up once or twice, not sure tho) however, since doing the vacuum lines, the pcv, and countless other upgrades/maintenance/repairs in the past month, i decided to get the codes checked and cleared to rectify any additional problems with the vehicle. so, after performing all the above mentioned work, the code reader pulls up just 1 code, to my complete surprise, a faulty TPS code. now, clearly it was a mistake, as the car was running just fine, so i just figured it was because i removed the throttle body etc etc to clean the area (while doing PCV work).

Now, heres the fun part...
the CEL stayed out for 2 days, no lights whatsoever on the dash (Cars been running like a dream) Unfortunatly, that ended yesterday on my way home from work when the CEL came back on. BUT this time was different. The light wasn't a SOLID CEL, instead, it flickered and dimmed frequently and has for the past day and a half. For example, if i lift the steering column all the way up, the light goes out, if i gently tap the dash or hit a bump, it flickers on and off. So, to be safe, i once again checked the codes only to find NOTHING. not a single code. the reader said PASS the 3 times i checked it. My question is, of course, what now? i have a mild case of OCD, so doing the repairs and getting that light out was a big deal for me, now it appears i've got a needle in a hay stack as both my neighbor and the auto store guy said theres probably a short somewhere. why me? why of all lights on the dash, the dreaded CEL?! haha please please please, if anyone has any input here, let me know whats up, because i need the peace of mind knowing that the light is not only OUT, but working properly. Thanks guys, sorry for the novel!

p.s. yes its a 94 and yes it came equipped with OBDII (thank God) The mileage sits at appx 235,000 right now.

p.s.s. Also regarding the pcv system cleaning, i still have white smoke essentially billowing out of the oil dipstick tube, however theres not enough crankcase pressure to "rattle" the oil cap when its just resting (un-tightened) on top of the engine. I read there should be a slight suction if anything, no outward pressure.mine still has crankcase pressure, or so it seems, but yet the car runs like a dream now with no stalling whatsoever. is this common? can something else cause the smoke? piston rings? seals?hopefully another case of my OCD making me nervous. the auto store guy checked it out and said it seemed normal & that i was just obsessing, but this is not normal, its pressure, its white smoke, and it's a steady stream. please contribute ; )



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Post by MadeInJapan » Sat Jan 12, 2008 10:26 pm

You said the TPS sensor code came on first...my thinking is that you have pulled on some wire that is now shorting or not making good contact during your PCV exchange. Check all of this...make sure it's tight...also, make sure your battery cables are corrosion free and tight. Once all of that is done, unhook your battery and push down on your brake pedal while it's unhoodked to do a hard "restart" on your ECU (sometimes prior ECU performance while things were "old" with the PCV, etc. can have lingering effects) and see how it goes. Don't forget, you'll need your radio code if you unseat your battery cable.


'98 S70 T5 Emrld Grn Met/Beige Tons of Upgrades Mobil-1
'04 V70 2.5T Red/Taupe Some Upgrades Mobil-1
'07 S40 T5 AWD 6 speed manual! Silver/Black Stage1 Heico & Elevate
'07 S60 2.5T Blue/Taupe- my kid's Volvo

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Post by smigg21 » Tue Jan 15, 2008 1:58 pm

Checked all connections and cant find any loose. checked codes again and still not a single one, it "passes" everytime. And the light is still intermittently on and off, flickering as if shorted out. last night it was off 90% of the trip, and bounced back on towards the end when i hit a bump. I read on other volvo forums that because its a '94 with OBD II, not all CEL codes are receiveable through OBD II Scanner, only engine related problems. The post said he had no codes with standard reader, but got 2 when he took it to volvo dealership. Has anyone ever heard of this?

UPDATE: Just spoke to Volvo Dealership. They want $75 for diagnostic check of the CEL (why not just buy the tool myself right?). Service rep said the 94's had a LARGE COMPOSIT THROTTLE BODY ASSEMBLY that was known for having AN INTERNAL FAULT which may be triggering the light. Has anyone ever read or heard of this issue?

UPDATE #2: Ok, did some investigative work, aside from searching forums, i called 20, YES 20, volvo dealerships across the country and finally found 1 who has had experience with this problem before. Mike @ Serafini Nissan-Volvo in NY is an electrical EXPERT, said hes worked on this a few times before and its a SHORT in the wiring harness that goes around the sterring column. He said its tough fix because so many wires and ur on ur head the whole time under the sterring wheel, but at least SOMEONE HAS SEEN IT BEFORE (4-5 times actually) WOOO HOOOOOOO! Saved me $75 at the local dealer for another "pass" diagnositic check. Ill be on "my head" for the rest of the night, Ill get back with my findings, cheers all!



MadeInJapan
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Joined: Thu Mar 31, 2005 7:14 am
Year and Model: '98 S70 T5 '07S40T5
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MadeInJapan

Post by MadeInJapan » Tue Jan 15, 2008 3:12 pm

I hope this guy is right about your troubles. Anyway, you said you have a '94 with OBD. However if your car is truly a '94 there are also diagnostic boxes under your hood- this is much better in my opinion than using the OBD connector. If you don't know about it, post again and we'll direct you to where they are and how to use them. Also, it would do you a world of good to download the service manual (free in the pinned section) if you haven't already done this.


'98 S70 T5 Emrld Grn Met/Beige Tons of Upgrades Mobil-1
'04 V70 2.5T Red/Taupe Some Upgrades Mobil-1
'07 S40 T5 AWD 6 speed manual! Silver/Black Stage1 Heico & Elevate
'07 S60 2.5T Blue/Taupe- my kid's Volvo

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