Help us help you. By posting the year, make, model and engine near the beginning of your help request, followed by the symptoms (no start, high idle, misfire etc.) Along with any prevalent Diagnostic Trouble Codes, aka DTCs, other forum members will be able to help you get to a solution more quickly and easily!
03 Tacoma 3.4L DOHC and it's shaking rattling and rolling. I posted about this truck already but want to avoid the information and brainstorming of the other post interfering or influencing here. I think I went down a few roads that I didn't need to and looked in a couple of rabbit holes that maybe had nothing to do with the issue at hand.
Here are my scanner results. Finally had the opportunity to start it and let it run though it did stall a couple of times. Not much difficulty restarting but the only thing I will say is it had an odor of "heat" despite temperature gauge and OBD2 showing normal. Some of the live data is not relevant but all the same I will post it. I will give codes which are P0300, P0301, P0304, P0031 I have absolutely no spark on cylinders 1 and 4. All the usual stuff has been tried. Looking for new direction and new ideas.
The truck had warmed up for 15 minutes and was idling when this live data was recorded. I'm wondering what is causing my open loop fault.
As usual I appreciate your help and any time that you put into this with me.
Otbrecords wrote: The truck had warmed up for 15 minutes and was idling when this live data was recorded. I'm wondering what is causing my open loop fault.
The majority of conventional O2’s are still capable of producing a decent signal with a blown heater element, provided the exhaust is hot enough. Not the case here. The heater HAS to be functioning, or the sensor will never work correctly. In fact, some vehicles will default to open loop fuel control with the presence of a heater fault.
As for the no spark, try the ScannerDanner bypass test: key on (powers up the coils and ignitor), backprobe at the ignitor on the IGT1 wire, touch backprobe with incandescent test light connected to battery positive and watch for spark at either #1 or #4 plug boot to ground.
If this works, then your ignitor and coil is fine. Focus goes to wiring to computer, or computer problem. I'm not sure if cam or crank would be suspect as you have spark on other cylinders and you have no cam or crank codes. It's got to be a wiring problem or computer problem I think.
Boy John you are the man. I had seen that ScannerDanner hack of manually firing coils not to long ago but couldn't remember exactly how to do it and I was having no luck finding it again. That was a test that I really wanted to perform, the one that I needed to complete the picture on the ignition system. As far as the scanner his concern, it's difficult to be confident in any mechanical device. I can't tell you that I hook it up to my Miata today, and with the new knowledge of reading fuel trims that I've recently gained I'm delighted that it's running great. It also verified that the scanner might be working well at least on the Miata because it's MAF was 0.48lb/sec. THANK YOU for sharing that thread that Tyler wrote on about heaters are not optional. That was a game-changer as well as everything else you've said today. Keep your fingers crossed I'll let you know how it goes I appreciate you.
Alright I had spark on ALL 6. I check them all just so I don't have to do it again. LOL Which means the IGT1 wire from the PCM to the igniter. Strange thing though, I've been here already. I tested that IGT1 wire for continuity and I get that under load stuff. So I spliced into it running a wire along with the original IGT1 wire and I understand the possible issues with doing it like that but still no "juice". So this I, I'm afraid to admit it out loud, CUT the wire leaving it short and splicin in a new wire but still nothing. Which you mean to tell me that it was either in the stubby wires left uncut at the connectors or the connectors themselves. Anyone have a video repairing or inserting wires into a harness? I need to also address my O2 heater and the MAF over-reporting. Thanks guys I really appreciate your help.
BUT BUT BUT... I put it all back together and back probed IGT1 at the PCM harness as well as IGT2 for comparison with engine on. IGT2 is pulsing at 3.9 volts and IGT1 has 0 volts. Just remember this is my second PCM that's doing the same thing. Now as a side note when I first got this second PCM IGT1 had 3.9 volts then it went away. At some point I back probe again and it showed lower voltage at 2.7 volts but now it's gone again. Either I'm crazy or something shutting it down. I did clear all codes before running this last test FYI.
Otbrecords wrote: I put it all back together and back probed IGT1 at the PCM harness as well as IGT2 for comparison with engine on. IGT2 is pulsing at 3.9 volts and IGT1 has 0 volts.
That's good you did that check at the PCM harness. Now, was it 0 volts because the wire was shorted? Connect a test light to battery positive and touch the wire. If it lights you have a short to ground.
While you're there, If you can make the ignitor fire the coils at the ignitor connector, but not at the pcm harness, then it's a wire problem.
As far as I know from ScannerDanner's videos, only the injectors get shut down to save the catalytic converter.
Ok I back probed IGT1 at ECU harness and was able to trigger coil. Sweet! ITG's on 03 Tacoma are "pull up" triggered. Consequently having a negative polarity with key on. Using positive test probe on all ITGs at ECU makes test probe light up but barely.
On a side note I back probed all four wires of A/F sensor B1S1 (2 black 1 white 1 blue wire) Here's what I got.
Key on - 12v on both black wires, other two had 3.3v & 3.0v
Key off - All 4 wires went to ground. Continuity between black wires only.
I think I'm going to throw my first part at this issue.. A new A/F sensor. Thoughts?
Thanks you Jreardom for the direction and education. I appreciate all the help from everyone.
Otbrecords wrote: Using positive test probe on all ITGs at ECU makes test probe light up but barely.
Okay so your test light is finding a ground through the computer maybe and that's normal. I can't let go of a hunch that this wire is touching ground somewhere intermittently when the engine shakes during the misfire, causing this signal to get pulled to ground.
Disconnect the Ignitor and the ECU. I'm interested in only one wire and I want you to check for an intermittent short to ground. Rig up your test light to battery positive and connect to any end of this IGT1 wire that's easiest to get to. Then I want to you slowly and gently push down on the harness everywhere you can see where the harness contacts metal. If the test light lights that indicates a short.
I’ve said the same thing checking that wire for a short to ground in the other post with the igniter and pcm unplugged using an ohm meter connected to battery negative or a loose terminal at the pcm.
Otbrecords wrote: Ok I back probed IGT1 at ECU harness and was able to trigger coil. Sweet! ITG's on 03 Tacoma are "pull up" triggered. Consequently having a negative polarity with key on. Using positive test probe on all ITGs at ECU makes test probe light up but barely.
On a side note I back probed all four wires of A/F sensor B1S1 (2 black 1 white 1 blue wire) Here's what I got.
Key on - 12v on both black wires, other two had 3.3v & 3.0v
Key off - All 4 wires went to ground. Continuity between black wires only.
I think I'm going to throw my first part at this issue.. A new A/F sensor. Thoughts?
Thanks you Jreardom for the direction and education. I appreciate all the help from everyone.
When it comes to 02 or AF sensor codes whenever it is a “heater circuit code” it is pretty accurate.
Something to consider though, while you were on the right track at testing the 2 black wires, you should be testing to measure resistance. A continuity test (I believe) if confirmed to have continuity will tell you that the circuit has 50 OHMS or less. 02 and AFrs should be 5 to 10 OHMS.
Making Pressure Differential Sensors (PDA Sensors) for pressure pulse diagnostics.
Currently servicing Central Texas.
John Curtis, Cheryl, Jreardom you and the others here on this forum give your advice towards diagnosis and it's appreciated as I'm sure you're aware. For me as well as others it your time, experience, and willingness to educate which is what I can't thank you enough for. My GF has the money to fix this but it was an opportunity for myself to sharpe my limited skills. This turned out to be a more than typical job, an opportunity that I'm thankful that I didn't pass up. So some are here to find a quick word to get them down the road or make some money while others are here for more. Throwing parts isn't only a possible waste of money but possibly a lost opportunity to learn and pick up some experience. All right enough with the Ramblin. Thank you, truly.
A week or so ago I cut out the IGT1 wire leaving enough on both sides to splice in a new wire. I might need to revisit this attempt. The new wire was not the right size being a little bit smaller. It didn't fix my issue so I splice back in the Old Wire like a dummy. I still wonder if the problem was in the part of the wire that I did not cut out. Despite all the other possibilities that I'm chasing down, the wire seems like the most obvious and still does. Also not clear if I reset trouble codes before deciding new wire was no good. You live and learn. Thoughts?
I'm fairly certain, as certain as one with my limited skill can be, that the A/F sensor is causing my open loop fault and possibly other things. Before I try a junkyard part or eventually new one, opportunity presents itself to learn something. The continuity between both black wires went to zero which if I understand is not what I want correct? How should I test it and what am I looking for exactly?
On a side note out of curiosity. My vacuum gauge test showed around 10 inches of mercury indicating a timing issue. Even though all marks are lined up and discounting a sheared key pin on crankshaft gear. I'm assuming that this no spark would cause the same vacuum symptoms? Since this all started after GFs brother replaced timing belt and knowing a torque wrench was not used. It's in the back of my mind whether or not vacuum is an issue because of a shifted gear. I observe no wobble in pulley but doesn't stop me from wondering.
Thanks for the reply. The MAF was the last part I looked at be for deciding the issues might be beyond my ability to fix this. I'm in the process of putting it back together. But here's what I have on MAF. 5 wires with 12v, 5v, signal, and 2 grounds that bother show continuity back to battery. It was my impression but only one was continuous ground and the other was signal ground? I would love for this to be the problem I'm having with the computer.
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