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ratrace2
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Mar 27, 2010, 8:37 AM
Post #1 of 15
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P0452 pcm/dtc error code
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1998 Chevy (2wd) s-10 (Ls) 2.2L (Ln2) automatic (M30)
Hello All,
I'm getting a P0452 error code from the PCM. (fuel pressure sensor)
I bought a new gas cap. . ..
I would like to start with the vacuum system and run through all the hoses and check for cracks etc. . .
I went ahead and got an "alldata" subscription for the truck for just such a task but I cant get an image of the system that is
good enough for me to make out where all the vacuum lines go.
maybe someone can help me find a better diagram, or something.....
thanks all..........
(This post was edited by ratrace2 on Mar 27, 2010, 8:43 AM)
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Sidom
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Mar 27, 2010, 7:04 PM
Post #2 of 15
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Re: P0452 pcm/dtc error code
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The P0452 is for the FTP sensor. The code sets if the signal goes below a predetermined value. Check and make sure you don't also have a P1639, this would indicate that the 5v ref is shorted to ground or power and would need to be traced down 1st before diag'ing the P0452...
Or if you just put a fuel pump in it......Then you need to plug the senor back in.........
(Not that I've ever done that...........I've just heard that  )
(This post was edited by Sidom on Mar 27, 2010, 7:05 PM)
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ratrace2
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Mar 28, 2010, 9:17 AM
Post #3 of 15
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Re: P0452 pcm/dtc error code
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The P0452 is for the FTP sensor. The code sets if the signal goes below a predetermined value. Check and make sure you don't also have a P1639, this would indicate that the 5v ref is shorted to ground or power and would need to be traced down 1st before diag'ing the P0452... Or if you just put a fuel pump in it......Then you need to plug the senor back in......... (Not that I've ever done that...........I've just heard that )
NOW:
What goes wrong to make the FTP switch voltage drop?
bad gas cap.
bad vacuum lines?
bad evap can. . .system...
hole in gas tank. . . .
Do we pressureize the system and look for leaks?
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ratrace2
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May 8, 2010, 12:08 PM
Post #4 of 15
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Re: P0452 pcm/dtc error code
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OK,
I finally got to put a digital multimeter (DMM) on the wire (gray) going to the fuel tank pressure sensor(FTP).
The meter showed 0.44 volts at the socket where the gray (5 volt reference wire) connects to the sensor.
Troubleshooting (testing for continuity).
I was thinking that I could put a DMM and check the voltage coming from pin 10 on the PCM/ECM.
If that was successful and I got 5 volts then I could run a wire from the sensor end to the PCM end and test for voltage from there.
Any ideas, guys.......
Thanks, RR2
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Sidom
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May 8, 2010, 6:00 PM
Post #5 of 15
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Re: P0452 pcm/dtc error code
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It sounds like you're on the right track.... Good job on tracking down the problem and not throwing parts at it....believe it or not but you are actually doing a better job on this problem then some techs in the field.
You need to backprobe pin #10 in connector C1 and check your voltage. It's probably going to read the same with the key on engine off as what you were reading down at the FTP connector (while it was disconnected)........
You need to find out if the wire is shorted and the 5v is getting pulled down or if you have a bad PCM....
If the voltage is the same at C1-10 with koeo. You need to remove the pin from the connector and check it again with the connector hooked up. If you now have 5v then the wire is shorted somewhere and should be traced down...I just did a real quick check and didn't see that 5v ref circuit sharing a signal with any other circuits but if there was a shared 5v ref circuit, that would have to be isolated as well.
What you are suggesting would work but I'm always leary of bypassing shorted power wires.... Where's it shorted? What else is going to short next? The same could be said about ground wires but personally I don't think it's as critical as power wires....
If you remove the wire and the voltage is the same @ the pcm with koeo then you are probably looking at a bad PCM.....
If you don't have the proper pin removal tools, you may have to cut the wire to isolate the circuit...... Well I don't like doing that it would be better to do that than damaging the pin in the connector. If you do decide to cut it, make sure you do a good job of hooking it back up, solder it, shrink wrap it and seal it the best you can..... you don't want corrosion getting into that circuit or that will open up a whole new set of problems..............
If you do get 5v @ the PCM with the circuit isolated..... You can take a test light hook the clip to the batt +, touch any ground spot (block, metal fender, anything) and make sure it lights up. Now touch the wire going to the FTP, if it lights up, you have a short. You can start wiggle the harness as you go back keeping an eye on the light. If it goes out or even blinks then thats the spot you need to check out....
You don't need to buy expensive backprobes..... Go to the ole lady's sewing kit and if she's got any of those pins with a T on the end, they work great..... She'll b*tch & moan but she'll get over it. I usually spray throttle body cleaner on the connectors weather packing and that helps the probe slide in real nice...... One tech suggested di-electric grease and that actually slides easier than throttle body clean, the only problem I had was weight of my scopes leads would would pull the probes out because it slide "too easy".
Also Staples sells them....Oh what that name...... They come in boxes of 1000, people use them for papers & ya gotta unroll them so their straight........
(This post was edited by Sidom on May 8, 2010, 6:10 PM)
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ratrace2
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May 11, 2010, 4:42 PM
Post #6 of 15
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Re: P0452 pcm/dtc error code
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I got a chance to start some more diagnostics.
I stuck my DMM probe into pin 10 of the ECM and got a solid 5 volts.......
DARN!!!. it would have been so easy to just go buy a new ECM/PCM. Now,
I have to track down a short (high resistance area) in the wire from one end of the truck to the other.......
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Sidom
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May 11, 2010, 8:51 PM
Post #7 of 15
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Re: P0452 pcm/dtc error code
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Sounds like you may have a broken wire. Usually the 1st thing I'll do is just do a visual on the wiring harnesses and see if there is any obvious damage or oil saturation that could've damaged a wire inside.... You may want to look around the back of the engine/bellhousing area
Maybe everyone will post some of the tricks they use.
I have a tool I use after it gets to the point where I'm going to have to start ripping harnesses open. Can't remember the darn brand name right now & couldn't find it on a google search but in a nut shell it has a small transmitter that puts a small amount of voltage in the circuit and a probe that picks up the voltage (thru the harness cover) and beeps. Just follow along the harness until it loses it's signal. you can go from either end of the circuit............. I don't use it a whole lot but it comes in very handy when I do need it. I've had it for long time but I think it was around 2 bills way back when.....
As anything, if you aren't going to be doing a lot of electrical work, it wouldn't be worth the investment..
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ratrace2
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May 12, 2010, 4:58 AM
Post #8 of 15
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Re: P0452 pcm/dtc error code
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SG2500 short finder is the one that is pictured in my Haynes Techbook "auto Electrical Manual.
They are getting cheap about $37.00.
I didn't know that oil saturation could short a circuit.
I think I'm going to run another wire and see If I can get the FTP working, then I'll try to get the wiring harness
repaired.
I might just get a new wiring harness. The truck is a 1998 Chevy S-10. When I pull out the motor and trans in the summer, I might as well do the wiring.
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Sidom
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May 12, 2010, 8:29 PM
Post #9 of 15
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Re: P0452 pcm/dtc error code
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Yes if too much oil from a leak or wherever constantly gets on a harness, it softens the wire insulation to the point that it just falls apart. You have a bunch of bare wires together & the rest is history...
GM on some of the older V/6s ran their crank sensor wires right under the oil filter. These were a/c sensors so the wires were twisted to shield interference. I can't possibly see any problem with that set up ..... Seen a few no starts come in with new crank sensors, ICMs, PCMs, etc & still wouldn't start....
Running a separate wire would be a good move to verify the circuit but I would probably still trace out the problem and fix it properly.....
The 1st circuit to go was the FTP sensor ref v.....which one will be the next to go?
Any electrical problem I get where I see a jumper wire run bypassing a circuit, I always compare that circuit to the one I'm checking in a schematic.... Those can be great clues.....
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ratrace2
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May 13, 2010, 12:42 PM
Post #10 of 15
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Re: P0452 pcm/dtc error code
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.................................All DTC's are Clear...................................................
.................................MIL indicator is OFF.............................................
Well, I went with plan B and ran a new 5 volt ref. line from the ECM to the FTP at the gas tank.
I just spliced into the connectors with new radioshack connectors. I only had 22ga wire, so I'll have to replace it soon.
But, the point is that the whole job really took my Diagnostic skills to a new level.....no more replace parts approach..
Man, Thanks so much to everyone.....Sidom, HammerTime. YOu guys are the best.
Total time to run the new wire and test if it would work was about 2 hours........
total cost of replacement/repair materials $10.00......
WOW, what an education that was.
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Hammer Time
Ultimate Carjunky
/ Moderator
May 13, 2010, 12:48 PM
Post #11 of 15
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Re: P0452 pcm/dtc error code
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Fantastic, Now your a real technician.
Everybody else would just keep changing the sensor and maybe eventually the PCM, all for a bad wire.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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ratrace2
User
May 13, 2010, 3:57 PM
Post #12 of 15
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Re: P0452 pcm/dtc error code
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You guys are the "real Techs". I know nothing compared to you guys.
I'm just fumbaling along reading books and trying testing equipment as I go.
But, I think I have the right "approach" and that is what, to me, counts.
I think it makes the difference between a "parts changer" and a "diagnostic Tech"......
Thanks All...............you Guys are the best................
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Hammer Time
Ultimate Carjunky
/ Moderator
May 13, 2010, 4:22 PM
Post #13 of 15
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Re: P0452 pcm/dtc error code
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Sidom is the best.
I often wonder where he gets his temperament and patience from.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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ratrace2
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May 13, 2010, 5:35 PM
Post #14 of 15
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Re: P0452 pcm/dtc error code
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I was thinking that same thing......................but you are really good too.................HT
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Sidom
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May 13, 2010, 9:18 PM
Post #15 of 15
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Re: P0452 pcm/dtc error code
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Good job on sticking with it and seeing thru to the end...... I know it's a lot of work and it can get real frustrating at some points but nothing beats that sense of accomplishment you get once you get it fixed.....
HT is exactly right about some people throwing everything including the kitchen sink at it and still not fixing it....
You went about this the right way, understood the system, tested it and based on your results went down the right path and was able to repair the problem..... That actually puts you ahead of some of the techs in the field (as far as diagnostics go). I know you have to figure your time but the materials cost of repair.......$10???? Man, most techs won't even walk out to the car for $10.......lmao
I appreciate the kind words and you taking the time to let us know the out come.....
That's the great thing about this place, there is a lot of experienced techs onboard here helping out and they've taught me a thing or 2 during the time I've been here.....
(This post was edited by Sidom on May 13, 2010, 9:20 PM)
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