94 b4000 cel on constant 335 code
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94 b4000 cel on constant 335 code
I have a 1994 Mazda b4000, 4.0L,manual, 4wd. 130k. (EEC-IV OBD 1). The cel light has been on for a long time. It still runs fine, starts good, never stalls, gas mileage normal. When I warm up the engine and pull the codes, the only KOEO self test code I get is a 335(egr sensor circuit voltage higher or lower than expected during self-test). A certified car mechanic I know hooked up his very expensive scan tool and got the same code and guessed that the dpfe sensor was probably the cause. I replaced the dpfe sensor. My cel is still on constant and when I pull the codes, I still get a 335. I checked the ref. voltage(vref) and I'm getting 5 volts. According to my repair manual it says that it should be between 4-6 volts, so it's within range. If I'm correct (correct me if I'm wrong) I have to be dealing with a wiring problem only, in the dpfe sensor circuit. If I'm getting the correct voltage to the dpfe sensor then where should I go from here. Checking the entire circuit all the way back to the pcm seems like it would be a pain, especially since the wiring runs underneath the upper intake manifold and back.
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From: Connecticut
Welcome. I've seen that code on similar-vintage Taurus and Sables. Even though the code appears to indicate a problem in the electrical circuit, sometimes it turns out to be clogged or split hoses, or coked-up EGR passageways (a/k/a "nostrils").
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no blockage
I pulled off the egr valve to check the passage ways and I didn't see any blockages in the valve or tube from the exhaust manifold, where it bolts to the intake,etc. I applied vacuum to the egr valve and it seems to be working fine. All the vacuum hoses seem to be in good condition, no cracks, etc. I do however have a 214(cid circuit failure) code (continuous memory code) which I didn't mention in my first post because I thought I should deal with the 335 code first. My code reader and repair manual both say to fix the KOEO code(s) first. That would be my 335 code. I'm wondering about the 214 code though. If my cam position sensor is shot and needs replaced and my PCM is operating in failure mode, shouldn't I be more concerned about that first? I haven't done a KOER test yet because the manual says to get a pass code 111 first on the KOEO test. I'm not sure it's operating in failure mode but I did erase the continous memory codes, started my truck, ran it for maybe 20 seconds and checked the codes again and got the 214 code again. Could a bad cam position sensor be messing with the PCM and it wouldn't know how to regulate the egr system? I don't know? Any advice?
Post Fiend
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From: Connecticut
I don't think the two codes are related. Regarding the EGR code, here are a couple of great resources regarding Ford DPFE/EGR System Operation & Testing:
http://www.tomco-inc.com/Tech_Tips/ttt35.pdf
http://www.tomco-inc.com/Tech_Tips/ttt36.pdf
I'm not 100% certain, but I believe on the '94 4.0L the CMP sensor and the CMP syncronizer shaft are integral to each other, so you might end up replacing the entire CMP assembly.
http://www.tomco-inc.com/Tech_Tips/ttt35.pdf
http://www.tomco-inc.com/Tech_Tips/ttt36.pdf
I'm not 100% certain, but I believe on the '94 4.0L the CMP sensor and the CMP syncronizer shaft are integral to each other, so you might end up replacing the entire CMP assembly.
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Thanks for the tech. tips that's exactly the info. I was looking for and I'd guess that would help me figure out my egr code. According to the tech. tips on ford egr systems I need to probe deeper into this, which I didn't do well enough. I'll check into it later this week, hopefully. I wish the weather would warm up, it's been TOO COLD.
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OK, I'll Post
What can I say, my cel is still on constant. I have recently pulled off the egr valve, again, to check for any carbon build up. I took off the tube from the egr valve to the exhaust manifold to check for any restrictiions( I blew it out with my air compressor and didn't find any signs of a clog.) I decided to replace my egr valve since I was taking everything apart anyway to eliminate the possibility of a sticking egr valve. It was the original valve with 130k. 40 bucks, what the heck. I checked the intake for any restrictions, none. Actually, I am very suprised at how clean everything is. I also pulled off the IAC solenoid to check for any blockages, it was suprisingly clean as well. I checked the upstream and downsteam hoses to the Dpfe sensor for any holes, none. My vacuum hoses seem to be in good condition, but I haven't really inspected them throughly, my truck's idle is smooth and I don't suspect a vacuum problem, but I will check them to make sure. I did run a koer test and got a 336 code (egr sensor circuit voltage higher than expected) and my ford code reader book includes an additional 336 R,C exhaust pressure high(trucks only) At this point, I really don't know?
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