ace4aday Posted September 4, 2007 Share Posted September 4, 2007 OK. Here's my story.....About a mile after filling up a nearly empty gas tank, my 98 Pathfinder quiet died at a red light. It started easily, but surged and slowed and quickly died, the CEL staying on. Visions of pumping out 20 gals of bad gas went through my mind. Luckily, we were only a half mile from home, a relatively straight shot with only two lights and we decided to risk it. We pulled into the driveway many stalls, starts, and a few horns and fingers later, and I proceeded straight to the toolbox. The scanner reported 3 codes, P0100 - Mass Airflow sensor or circuit fault; P0325 - Knock sensor or circuit fault; and a P0100 Pending (I have no idea what Pending means). I start it up and it runs for a couple of seconds and dies. I pop the hood and start it up and it runs with the rpm constantly changing. There is also a tick tick ticking sound in time with the engine, similar in sound to a small electric discharge, coming from the area of the EGR valve. I shut everything off and clear the codes. I turn the vehicle on a it sounds great, strong, no ticking, nothing. I let it run for awhile and then hop in for a run up the street. I got to my turn around point and it dies. I limp it back home again. The P0100 error is back and so is the ticking. While checking out the MAF, I notice I can sometimes kill the engine just touching the MAF or by just grabbing the wires behind the plug and wiggling very lightly. Now I wondering...bad gas? Bad MAF? Bad connectore? Bad wiring harness? I clear the code, and it doesn't always come back just by me killing the engine while playing with the MAF or the connector. Next, I disconnect the harness and check the power and ground circuits to the sensor and got a nice even 12v. I reconnect the harness and back probe the signal wire. I get about 1.3v at idle and it runs up to about 1.8v at 2k rpm. Finally, I crawl under the dash and disconnect the wiring harness from the ECM. I checked continuity of the white and black signal wires between the MAF connector and the ECM harness while aggressively twisting and bending the MAF end of the harness and connector. The constant annoying whine of my DMM confirms the wiring harness and connector to be in good shape. I plug everything back in, clear the codes, and start her up. She sounds nice until I touch the MAF wires which kills it instantly. The tick (and the P0100) is back when I start it up. So here are my questions: 1) Do MAF's die suddenly? Is a dying MAF so sensitive that just touching it or the wiring harness cause everything to fail? Can I rule out the gas? Should I have the MAF itself further tested? Should I try cleaning it? Should I just break down and change the MAF and hope that was it? Did the MAF problem cause the P0325 (which never came back)? Help! Link to comment Share on other sites More sharing options...
lunchindabox Posted September 4, 2007 Share Posted September 4, 2007 So here are my questions: 1) Do MAF's die suddenly? YES, i think 2.Is a dying MAF so sensitive that just touching it or the wiring harness cause everything to fail? YES, i think 3.Can I rule out the gas? YES 4.Should I have the MAF itself further tested? YES 5.Should I try cleaning it? YES 6.Should I just break down and change the MAF and hope that was it? AFTER THE CLEANING AND HARNESS CONNECTIONS ARE TRIED/TESTED. 7. Did the MAF problem cause the P0325--- NO.(which never came back)? Help! DONE. Post your results buddy. Link to comment Share on other sites More sharing options...
88pathoffroad Posted September 4, 2007 Share Posted September 4, 2007 Good points. If the MAF code came up and wiggling it makes it die, I'd suspect it went wacky on ya. Take 5 minutes to unscrew it and pull it out, see if both wires are intact or perhaps gummed up with some debris. The knock sensor code is very very common and that damn thing is very very difficult to replace. Most people just leave it alone unless it's causing/allowing detonation. Link to comment Share on other sites More sharing options...
ace4aday Posted September 5, 2007 Author Share Posted September 5, 2007 (edited) I pulled the MAF and did a visual. The wires and filaments? appeared to be intact, but the one towards the rear of the unit was coated with grime. I sprayed it off with contact cleaner, let it dry, and reinstalled it. When I started my rig, it ran for a few seconds and died. If I tried to run the engine up a little, it started chugging like a train before eventually stalling. I went and picked up a re-manufactured MAF from Schucks ($134 + $55 core) and popped it in. Started right up and ran like a champ. Took it for a spin with no issues. Problem solved! Thanks for your comments 88pathoffroad and lunchindabox. Edited September 5, 2007 by ace4aday Link to comment Share on other sites More sharing options...
lunchindabox Posted September 14, 2007 Share Posted September 14, 2007 I pulled the MAF and did a visual. The wires and filaments? appeared to be intact, but the one towards the rear of the unit was coated with grime. I sprayed it off with contact cleaner, let it dry, and reinstalled it. When I started my rig, it ran for a few seconds and died. If I tried to run the engine up a little, it started chugging like a train before eventually stalling. I went and picked up a re-manufactured MAF from Schucks ($134 + $55 core) and popped it in. Started right up and ran like a champ. Took it for a spin with no issues. Problem solved! Thanks for your comments 88pathoffroad and lunchindabox. Glad to hear your up and running again (without paying "diagnostics"). Link to comment Share on other sites More sharing options...
Destro Posted September 14, 2007 Share Posted September 14, 2007 7. Did the MAF problem cause the P0325--- NO.(which never came back)? It could have, the malfunctioning MAF could have caused the knock sensor to retard the timing. The knock sensor code doesn't necessarily mean the knocks sensor is bad, it can mean that the knock sensor is just detecting knock and therefore it started working. More than likely, when you fix the maf problem and clear the codes, the knock sensor code won't come back. Link to comment Share on other sites More sharing options...
XPLORx4 Posted September 14, 2007 Share Posted September 14, 2007 The knock sensor code doesn't necessarily mean the knocks sensor is bad, it can mean that the knock sensor is just detecting knock and therefore it started working. Actually, that's not correct. The knock sensor code means the knock sensor is not operating normally. What you just described above depicts normal knock sensor operation, which won't trigger the code. Link to comment Share on other sites More sharing options...
Destro Posted September 14, 2007 Share Posted September 14, 2007 We see the knock sensor code all the time with a MAF code or misfire or something like that. We fix the other problem, clear the code, and the knock sensor usually never comes back. Unless there really is a problem with the knock sensor. Link to comment Share on other sites More sharing options...
lunchindabox Posted September 14, 2007 Share Posted September 14, 2007 We see the knock sensor code all the time with a MAF code or misfire or something like that. We fix the other problem, clear the code, and the knock sensor usually never comes back. Unless there really is a problem with the knock sensor. I am going to have to agree with EplorX4 on this one...I think most people don't check the codes after the light goes out and I think we can all agree that a knock sensor will not throw a CEL only a code. And what he tells makes sense, that is the normal operation of a KS IMHO Link to comment Share on other sites More sharing options...
Destro Posted September 14, 2007 Share Posted September 14, 2007 I am going to have to agree with EplorX4 on this one...I think most people don't check the codes after the light goes out and I think we can all agree that a knock sensor will not throw a CEL only a code. And what he tells makes sense, that is the normal operation of a KS IMHO yes, but we are actually rechecking for any codes after the repairs are done, and the knock sensor code does not come back, unless there really is a problem with the knock sensor. Most of the time the code never comes back. Link to comment Share on other sites More sharing options...
XPLORx4 Posted September 14, 2007 Share Posted September 14, 2007 (edited) yes, but we are actually rechecking for any codes after the repairs are done, and the knock sensor code does not come back How do you you check for codes after the PCM reset? According to the service manual, the KS has "one-trip detection logic", and "a "trip" means "a driving mode in which self-diagnosis is performed during vehicle operation." However, it's not clear from the FSM exactly which "driving modes" actually initiate self-diagnosis. Since the KS code doesn't trip a MIL, it's entirely possible that the knock sensor DTC will trip after you have returned the vehicle to the customer, and the customer would never know, nor bring it back to you for repair since there's no MIL. Edited September 14, 2007 by XPLORx4 Link to comment Share on other sites More sharing options...
lunchindabox Posted September 15, 2007 Share Posted September 15, 2007 How do you you check for codes after the PCM reset? According to the service manual, the KS has "one-trip detection logic", and "a "trip" means "a driving mode in which self-diagnosis is performed during vehicle operation." However, it's not clear from the FSM exactly which "driving modes" actually initiate self-diagnosis. Since the KS code doesn't trip a MIL, it's entirely possible that the knock sensor DTC will trip after you have returned the vehicle to the customer, and the customer would never know, nor bring it back to you for repair since there's no MIL. Correct me if I am wrong.... One-trip logic means that it is tested with one drive (start engine, reach operating temp, stop engine) Other sensors like o2 take several trips or drive cycles to be "ready" and if they come up good, no CEL...if they come up bad..you get a CEL when ever the ecu decided it has enough data to have correctly diagnosed the fact that there is an issue. "One trip" means the ecu decided based on one trip. In short...I think alot of these folks do not know they have that code at all, including the ones who think they fixed it. The only way to be sure it it fixed is to hook up a ODBII scanner after "one trip" which I suspect many people don't do. But Destro sounds like a tech that does check the codes, so i would rather take his word as i am just speaking on my own little peice of expereince. I would however like to see the ace4aday put a scanner to his and see if the code is in the computer and there is no MIL...like mine. The KS does not trip a MIL/CEL. When i bought my R50, it had 3 codes...I reset the ECU and after a drive around the block I hooked up my crappy 100 dollar scanner and it had detected the KS but not the Evap or 02. I tried to go through emmisions and of course they said I needed to go through more drive cycles before it was ready to be tested. Here is a little unrelated hint that saved me a few hundred dollars. I had a damn Ford that failed the smog test due to MIL...and I reset the damn ECU and took it back..."not ready" I hooked up my scanner...drove around until 4 of the 6 sensors were ready...and no light..this was my window od oportunity to pass emmisions, the fifth or 6th was going to throw a code You see, for ODBII cars between 96 and 98, you can have 2 sensors "not ready" or not have enough drive cycles to determine good vs bad and throw a MIL. For 99 and up, all sensors but 1 has to be ready. When I drove off from the station after passing, the damn light came back. Lucky me. 1 Link to comment Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now