MrT Posted May 28, 2011 Share Posted May 28, 2011 http://www.harborfreight.com/7-function-digital-multimeter-90899.html Look at it this way. You'll save the money you spend on this in gas by not having to drive around seeing if the things you did had any effect. You won't regret it. It's the ONLY way to accurately trouble shoot wiring. 1 Link to comment Share on other sites More sharing options...
NissanNismoZ Posted July 17, 2011 Author Share Posted July 17, 2011 (edited) Okay..so i bought a multimeter..where do i start? I tried checking for voltage from the MAF plug..but i get nothing.. (i could be doing something wrong) I'm pushing the pin in the pins on the maf plug and grounding the other one on the engine..and hoping for voltage..is that right? If so..how do i check the maf with the plug plugged in? coz i dont see how you can check the maf, running.. Thanks! i do know the ground i added only has .02 ohms resistance..so im assuming that's alright.. but..any ideas?? Thanks Im assuming itll be the samev way to check my idle switch.. if those come up alright or something wrong, ill check the injectors for resistance? EDIT Shoved prong down inside MAF connector..and grounded the other prong..i can get around 1.0-2.5v from the maf when revving it..so its putting out voltage..so..it shouldnt be sending out a code..right? Checked all injectors..except 4 and 6.. all read 13.8-14.0 ohms resistance i know this doesnt help, but ill add the voltages of 4 and 6 when i can figure out how to reach them.. #4 was the injector i replaced before buying it.. Edited July 18, 2011 by NissanNismoZ Link to comment Share on other sites More sharing options...
MrT Posted July 18, 2011 Share Posted July 18, 2011 Check pins 16 & 17 at the ECM for the proper voltage. It could be an issue with the wiring in between the MAF and ECM. Just to add to your frustration, by the nature of an intermittent electrical problem it probably isn't doing it when you're testing it. The only thing I can suggest is to test at the ECM and then drive around watching the voltage to see if it will cut out. When my MAF was bad it wasn't "always" bad. It picked and chose when it wanted to work. Link to comment Share on other sites More sharing options...
NissanNismoZ Posted August 27, 2011 Author Share Posted August 27, 2011 (edited) Check pins 16 & 17 at the ECM for the proper voltage. It could be an issue with the wiring in between the MAF and ECM. Just to add to your frustration, by the nature of an intermittent electrical problem it probably isn't doing it when you're testing it. The only thing I can suggest is to test at the ECM and then drive around watching the voltage to see if it will cut out. When my MAF was bad it wasn't "always" bad. It picked and chose when it wanted to work. Okay..now that i've gotten a few of my exterior (easier) things fixed, im back to tracking these down. How do i count these at the plug? I added a new ground to my MAF sensor and..somehow that screwed up my security system.. Thanks! I just dont get how, on long trips (over 40 miles, or so) the CEL goes off and stays off. I even went through the extent of leaving it disconnected over night..still shows the same codes, so im going to have to tear into the dirty part and get specific.. But..one thing i dont understand.. if it has ALL these codes.. what makes the light even come on? surely they cant just all stop malfunctioning at once..can they? My codes still stand at: 12 Air Flow Meter/Mass Air Flow Sensor. 51 Injector Circuit. 45 Injector Leak. 34 Knock Sensor. 23 Idle Switch. Edited August 27, 2011 by NissanNismoZ Link to comment Share on other sites More sharing options...
NissanNismoZ Posted August 29, 2011 Author Share Posted August 29, 2011 Removing the part of the exhaust that kept banging on the muffler fixed my knock sensor code... Link to comment Share on other sites More sharing options...
MrT Posted August 30, 2011 Share Posted August 30, 2011 Check the voltage at the MAF while the engine is running. You need to back probe the connector on the MAF. To do this you very carefully wiggle the leads of your meter under the weather sealed connector pins. I've got an R50 so I can't really show you with a picture. It has three wires. Voltage supply, voltage return and ground. You want to check the supply and return individually with your meter set on VDC. Link to comment Share on other sites More sharing options...
NissanNismoZ Posted August 31, 2011 Author Share Posted August 31, 2011 Done! My results are: Maf idle = 1.58v Maf 3k rpm = 2.55v stable MAF reference = 13.88v (shouldnt that only be 5v??) Link to comment Share on other sites More sharing options...
NissanNismoZ Posted August 31, 2011 Author Share Posted August 31, 2011 Spent 10$ on a MAF from a paths pathy..well... put it in, drove it until the CEL came on (only about a mile) checked the codes, and still throwing the same codes..so im guessing this means im looking into even deeper troubles.. Link to comment Share on other sites More sharing options...
ejin4499 Posted August 31, 2011 Share Posted August 31, 2011 Spent 10$ on a MAF from a paths pathy..well... put it in, drove it until the CEL came on (only about a mile) checked the codes, and still throwing the same codes..so im guessing this means im looking into even deeper troubles.. I'm thinking you need to pull the passenger seat put your multimeter to the pins on the ECU and see if you can find a discrepency between whats coming out of your sensors and whats going back to the ecu. It doens't sound like a problem with the maf sensor itself to me. Link to comment Share on other sites More sharing options...
NissanNismoZ Posted September 1, 2011 Author Share Posted September 1, 2011 Okay..let me change that a bit.. so i found out how to clear my codes (i thought you had to disco the battery, then reconnect and drive..) so i clear them, start it up, go on a 30 mile drive, driving it extremely hard (nothing over 4k rpm though) and.. no codes! the CEL doesnt even come on when i first turn the key..maybe the new MAF fixed it? Will try what you said if the light comes on again..but until then..thanks everyone!!! Link to comment Share on other sites More sharing options...
NissanNismoZ Posted September 2, 2011 Author Share Posted September 2, 2011 I should have known that was way too easy.. CEL is back... -.- so.. I'm going to try to check the pins on the ECU, as mentioned..but..i dont know how you count them?? Even after the (over 40 miles now) of no CEL, it comes back, first thing when i start it up today.. Same codes as before..im leaning toward it really being the same problems..or..it being a bad ECU. (too expensive, so going to do diagnostics for now..) Thanks everyone! Link to comment Share on other sites More sharing options...
sewebster Posted September 2, 2011 Share Posted September 2, 2011 pin out in fsm Link to comment Share on other sites More sharing options...
Slartibartfast Posted September 2, 2011 Share Posted September 2, 2011 To go back a few posts... you said the light goes out after you've been driving a while. I assume that this driving is highway, and at speed... suggests to me that the problem either occurs during acceleration (but not when holding speed) or before the car has fully warmed up. Of course, I have no idea what that would point to. Also, is the engine acting up when the CEL's on? My understanding is that when the MAF goes out, the engine sputters and coughs black smoke and generally lets you know that something is horribly awry. If the only symptom is the light coming on, maybe something else is acting up and posting your various codes. And while I'm pretending I know what the hell I'm talking about... any chance you've got a bad seal on the gas cap? My friend freaked out and thought her Pontiac was breaking down because the CEL came on, turned out she just hadn't screwed the cap in. Having somehow never forgotten my cap, I don't know if Nissans do the same thing. Link to comment Share on other sites More sharing options...
adamzan Posted September 2, 2011 Share Posted September 2, 2011 (edited) I don't think wd21s have the ability to tell if the gas cap is not on properly. I think that all started with obd2. Edited September 2, 2011 by adamzan Link to comment Share on other sites More sharing options...
NissanNismoZ Posted September 2, 2011 Author Share Posted September 2, 2011 Hmm..honestly the engine drives the same..i notice zero change in performance from when its running all day without a CEL and when it has a CEL..that's why im so confused.. Ill check all my connections at the ECU when im home.. coz its bothering me..even though im leaning toward a ground somewhere.. Link to comment Share on other sites More sharing options...
Alkorahil Posted September 2, 2011 Share Posted September 2, 2011 (edited) Knock sensor... don't worry about it yet. That code pops up whenever there's another code for the most part. I was going to say the same thing. A malfunction causing the engine running super rough will casue a Knock sensor code to go off as well. However, looking at all these codes, hwat codes you are getting all at once, which are really unrelated, and your mentioning a pinched wire(s) I am wondering if you have perhaps an engine harness problem where the whole harness is grounding signal out signal intermittantly and confusing the ECU abd causing the CEL to go on.... Edited September 2, 2011 by Alkorahil Link to comment Share on other sites More sharing options...
ejin4499 Posted September 3, 2011 Share Posted September 3, 2011 Hmm..honestly the engine drives the same..i notice zero change in performance from when its running all day without a CEL and when it has a CEL..that's why im so confused.. Ill check all my connections at the ECU when im home.. coz its bothering me..even though im leaning toward a ground somewhere.. IIRC the pinout on the ecu harness is as you look at the harness from the front. So you would actually disconnect the harness from the ecm and count your pins from the front of it. Link to comment Share on other sites More sharing options...
NissanNismoZ Posted September 6, 2011 Author Share Posted September 6, 2011 so..would it be like.. 1357 2468 or.. 1234 5678? just wanting to get this right..thanks!! Link to comment Share on other sites More sharing options...
NissanNismoZ Posted September 8, 2011 Author Share Posted September 8, 2011 Okay..so after an hour of looking through the FSM..i found out it was in the electrical foldout..and not the electrical section..heh. (You know what they say about assuming.....) So i'm supposing ill be pulling the seat tomorrow and checking to see what pins 16 & 17 say actually..i remember when i first started fixing the pathy (before i bought it) the ECU was laying there unbolted and unplugged...) last i remember there were a lot of extra plugs under there...are those just extras or something? I'll post more specific information on that tomorrow with a picture.. and im also no longer saying "my CEL is gone" until i get 500 miles of no CEL! it keeps getting my hopes up for no reason... Link to comment Share on other sites More sharing options...
NissanNismoZ Posted September 8, 2011 Author Share Posted September 8, 2011 Woo! Okay..i did it.. Here's the information i got: Pin 16 (Idle) .07v Pin 16 (2000 RPM) .10v Pin 17 (Idle) 13.17v Pin 17 (2000 RPM) 12.75v What exactly are pin 16 and 17? 16 seemed to act like the MAF (increases on throttle) 17 acted..odd. the harder i pushed on the pedal, the voltage went down?? Thanks everyone..i really appreciate the help!!! Link to comment Share on other sites More sharing options...
NissanNismoZ Posted September 12, 2011 Author Share Posted September 12, 2011 In further news, someone recently told me about my rear speaker wires running beside the ECU could be causing interference and causing a CEL? It is odd that after having the radio off for a while, the CEL went off. BUT. im not saying this is the fix until i hit another 1000 miles with no CEL. Does anyone else agree this could cause interference? Or is the ECU too shielded for that? Thanks! Link to comment Share on other sites More sharing options...
sewebster Posted September 12, 2011 Share Posted September 12, 2011 Might want to put a tinfoil hat on your ECU, just to be safe. Link to comment Share on other sites More sharing options...
NissanNismoZ Posted September 13, 2011 Author Share Posted September 13, 2011 LOL i hope you're joking and im not laughing at good advice.. anyway, as i figured, it's back! Link to comment Share on other sites More sharing options...
sewebster Posted September 13, 2011 Share Posted September 13, 2011 Link to comment Share on other sites More sharing options...
MrT Posted September 18, 2011 Share Posted September 18, 2011 In further news, someone recently told me about my rear speaker wires running beside the ECU could be causing interference and causing a CEL? Your ECU is designed by engineers who know what shielding is. While not impossible I find this extremely unlikely. If anything the ECU would cause interference in your speaker signal. Link to comment Share on other sites More sharing options...
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