Hello, I was looking at the pdf that Carpedal posted for the 2010 wiring diagrams and wondering if anyone knows what these codes mean on the wires. Also, the MAF sensor has five pins, but the diagram has four. Thanks.
The letter codes shown on the wires are the colors: B for black, BR for brown, etc. There should be a list of those near the front of the wiring diagram. The numbers shown outside the boxes where the wires join are the terminal number at the respective connector. So the terminals of the MAF, in order, are purple/THA, brown/E2, black/+B, white/E2G, and black/VG. (By my count, that's five.) The codes shown inside a component where the wires attach don't appear in some official list of meanings; those are mnemonics that should jog your mind into guessing what their roles are in the circuit. The more you know about the circuit, about electronics in general, and the way Toyota folks dream up mnemonics, the more effectively they jog you. For common examples, +B is one you will see very very often that means exactly what you probably think, and mnemonics that start with E will often be ground (many places say 'earth', even though a mobile car has nothing staked into the earth!). The best way to make sense of the mnemonics is to not just look at the diagrams in the Electrical Wiring Diagram, but to study them together with the ones in the Repair Manual. For the MAF, you'll find those in the workup steps for P0102/P0103 and for P0112/P0113. The first two codes are for the airflow reading, and the diagrams there show +B, VG, and E2G. The latter codes are for the intake air temperature reading (the MAF sensor does that too), and the diagrams there show THA and ETHA. You'll be getting the idea that there still isn't a list anywhere that says "hey, VG means this and THA means this", but when you see them used in circuit schematics and in steps of test procedures given with outcomes that tell you what's wrong with what, you start to piece together what they are mnemonics for. So you'd probably gather that THA is their name for the air temperature THermistor circuit, and ETHA is that circuit's ground reference, and VG is the Voltage that indicates the air flow reading, somewhere between +B and its ground reference E2G. Sometimes you'll notice different mnemonics at the two ends of a wire: what the team that designed the ECM called ETHA, the team that designed the MAF sensor called E2. Stuff like that happens. Another thing you'll start to notice is that the most common 'ground' connections all over the car are usually white wires with black stripes, but the critical underhood sensors are usually grounded by brown wires that make up their own isolated ground reference (hence "E2", I think), to keep sensor readings free of the electrical noise generated by all the other gunk using the white-black grounding network. And occasionally some very privileged sensor will get its very own exclusively dedicated ground, like E2G here, inside a grounded shield, no less.
@ChapmanF covered the basics, but I’ll add two points: The circled letters, such as Ⓑ near 116 and THA on the engine control module, are used when a part has more than one connector. These will be listed near the part name; where the Mass Air Flow Meter has “D5,” for example, the ECM has “A57(A) D28(B),” which means that wires to the ECM shown with Ⓐ go to connector A57 and wires to the ECM shown with Ⓑ go to connector D28. Thus, the wire with pink insulation goes to terminal 116 on connector D28. The functions of the terminals, if not the origins of their mnemonics, are often explained in the Repair Manual, in the Terminals of ECU (or Terminals of ECM) pages for each system. For many terminals, those pages also tell you what voltages or waveforms you might expect to measure under specified conditions. Some of the mnemonics are fairly obscure: AM, AM1, and AM2, for example, are a legacy of designs in which the common terminals of the ignition switch were connected to the A(m)M(eter). You won’t find an ammeter on any Prius car, and the ignition switch has been gone since model year 2004, but the names live on.
I appreciate the fact you have gone thru the trouble of uploading all those files into Acrobat. However, I have had no luck downloading. The download indicator goes round & round with no result. Would you consider uploading to Google Drive? Thank you in advance!
Anyone else having issues downloading the files from the link on last page? Regardless of what I try for browser/computer I cant get the link to work.
Because my TIS subscription isn't paid up at the moment, I looked for the code in one of the PDF repair manual copies floating around, but the one I looked in seems to be missing the detailed workup sections for P3107. (That happens sometimes, as the PDF copies usually came from somebody signing in to TIS and clicking Print a whole lotta times, and maybe their eyes glazed over at some point in the middle.) Sometimes the best way forward is just to pay the $20 for TIS access for a couple days. It definitely beats paying a dealer $120 an hour until they figure something out. Does this help with locating L16?
Hey there, do you still have the PDF's of the service manuals? I'm trying to find them! No luck anywhere. And your adobe links dont work anymore. Would you be willing to re-upload them? It would be greatly appreciated. Adam