MAF blowing fuse
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Teching In
Joined: Oct 2018
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MAF blowing fuse Trying to fix someone else's project LS swap. New rewired stand alone harness had the engine running fine then suddenly engine died from a blown ECM fuse. Traced the short to the MAF. Unplug the the MAF and short goes away but engine runs like ***(for obvious reasons). MAF is good. Disconnect the pink MAF wire from the harness, plug-in the MAF, and the engine runs perfect. My questions: How did this pink wire from MAF suddenly short out? How is the engine receiving a signal from the MAF when the pink supply wire is disconnected from 12v?
If you unhook the pink wire and it doesn't blow the fuse, then the pink wire isnt shorted, it's going to be one of the 2 that go to the pcm that are not the temp sensor wires. It probably runs better with just the one wire unhooked but with the MAF plugged in because the intake air temp sensor is plugged in.
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If you unhook the pink wire and it doesn't blow the fuse, then the pink wire isnt shorted, it's going to be one of the 2 that go to the pcm that are not the temp sensor wires. It probably runs better with just the one wire unhooked but with the MAF plugged in because the intake air temp sensor is plugged in.
Is there anything else that the pink wire is feeding that could be at issue? On factory GM harnesses the O2 sensors are also fed from the same fuse as the MAF sensor. When you say you have removed the pink wire, are you just removing it from the MAF sensor? As a test you could unplug all O2 sensors and then test again.
Is there anything else that the pink wire is feeding that could be at issue? On factory GM harnesses the O2 sensors are also fed from the same fuse as the MAF sensor. When you say you have removed the pink wire, are you just removing it from the MAF sensor? As a test you could unplug all O2 sensors and then test again.
Forgot to mention that air temp switch is in the MAF. Using a test light I can prove that the pink wire is shorted with the MAF plugged in. When I unplug the the MAF the test light goes off. But I think I understand what you're saying. 5 wires on the MAF plug. The pink supply wire(disconnected to keep from blowing fuse), 2 grounds, signal, and 12v. You're saying that either signal or 12v wire is shorted.?
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Here's the diag procedure I performed when I had the blown ECM fuse. Tested each wire that was on the blown circuit. Determined what wire was shorted and followed it. That wire had a splice that split into 3 wires(all pink). Separated those three wires and tested each one to determine the short. Spliced the other 2 wires back into the circuit and replaced the fuse. Only 3 things could have been on that shorted pink wire-O2's, MAF, and transmission. With my test wire clipped on the end of the pink wire that is disconnected, I unplugged each one of those until the test light went off. BINGO, the MAF is the culprit! I installed a good MAF and still have the short.
If I leave the MAF plugged in the engine runs good. Unplug the the MAF and short goes away but engine runs like ***(for obvious reasons).
If I leave the MAF plugged in the engine runs good. Unplug the the MAF and short goes away but engine runs like ***(for obvious reasons).
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Your engine should not "run like ***" when the MAF is unplugged. If you notice a big change in how the engine runs when the MAF is unplugged, then you have tuning issues ahead of you. Without the MAF, the PCM relies on the VE table to run the engine. If that table is RIGHT, then unplugging the MAF will have little to no effect on the engines idle, and running, characteristics.
I understand you are just focusing on the dead-short at this time so I hope my post is not adding further confusion to your challenges. Just plan on tuning this vehicle when you get the short sorted out because based on what you are saying-the VE table is not right.
I understand you are just focusing on the dead-short at this time so I hope my post is not adding further confusion to your challenges. Just plan on tuning this vehicle when you get the short sorted out because based on what you are saying-the VE table is not right.
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Verdad Gallardo Here's the diag procedure I performed when I had the blown ECM fuse. Tested each wire that was on the blown circuit. Determined what wire was shorted and followed it. That wire had a splice that split into 3 wires(all pink). Separated those three wires and tested each one to determine the short. Spliced the other 2 wires back into the circuit and replaced the fuse. Only 3 things could have been on that shorted pink wire-O2's, MAF, and transmission. With my test wire clipped on the end of the pink wire that is disconnected, I unplugged each one of those until the test light went off. BINGO, the MAF is the culprit! I installed a good MAF and still have the short.
If I leave the MAF plugged in the engine runs good. Unplug the the MAF and short goes away but engine runs like ***(for obvious reasons).
If I leave the MAF plugged in the engine runs good. Unplug the the MAF and short goes away but engine runs like ***(for obvious reasons).
Thread Starter
Teching In
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Update. I'm still stumped. I test the 2 signal wires (IAT tan, MAF yellow) like LS1nova71 suggested and neither wire is grounded. After more testing I discovered that with the MAF connected the pink wire (12v power) completes the circuit to ground thru the ground wire (black). How is this possible? I thought maybe the connector was bad so I test with a different connector but same result. Out of desperation I cut the ground wire and connected the pink wire back to 12v. Engine idles great but no power and slow to rev. I thought that maybe the MAF had shorted but 2 different MAF's had same results(one MAF is off my daily driver).
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Joined: May 2021
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From: Imperial valley, CA
My solution hi everyone I have been working on a third Gen Iroc LS2/4L70E swap and had similar problems after hooking up the maf. I used this for reference and like to share my solution since I wish I heard back from this one.
We had been running the engine before with no problems although my buddy did arc a wrench to ground after we forgot to disconnect the battery when relocating the racetronix fuel pump wire. The engine ran ok after replacing a couple of fuses after that, once the maf was plugged in the aftermarket stand alone fuse box kept blowing the maf/iat 15A fuse. we checked anything relevant to the circuit found the 12V pink wire from terminal D on the connector to have a short to ground. We couldn’t find anything damaged . After feeling stumped (not having a wiring diagram sucks as well) I called tech support from the company we got the harness from, after some back and forth he told me to check the connector & de- pin the 12V pink wire or cut it, which I had to do because after trying to de-pin it...I could not pull it out! After I simply cut the wire the engine started!! I ordered a connector and will test out the Maf to see what caused the connector to short out.