Am I missing a relay?

Mine is in 09 loaded but is not a tourer or have fog lites. My fuse box picture looks exactly like yours and my car's been running perfectly for years like 20 I have the ABS problem too and I know my pump and accumulator or bad have some sort of an internal leak causing a left rear low pressure code i'm scared to try and fix it because of how long the car might be down my brake pedal works fine I don't have true abs but my pedal pressure is good and the car stops very well on my other car exactly like this when the brakes went bad it took two people to stand on the brakes to make the car stop of course that car we stopped driving this car the brakes have remained perfect you are missing nothing in that picture of your fuse box it looks just like mine I can't post it here

 

What code do you have? I would suggest following the diagnostic steps for that code in the service manual.

There are an awful lot of relays in a Gen2 Prius- having something to guide your checkout will likely speed up the process by focusing on specific circuits related to the fault code.

Posted via the PriusChat mobile app.

 

Per the OP's earlier thread, a C1241, accompanied by C1310, C1343, C1344.

I suggested troubleshooting the C1241 first, then seeing which of the other codes return. The INF code for the C1241 would be helpful, given a scan tool able to read it. The repair manual and wiring diagrams (more info) have troubleshooting steps and needed info for tracing the C1241 issue.

It is helpful to keep the troubleshooting of a single issue together on a single thread, so losses of context like this don't happen.

 

Just off the top of my head, and anyone correct me if I'm off base, two relays supply the ABS. Without having studied the schematics, but reading the code info, I've looked at it as a redundancy thing. If one takes to long to pull in, sets a code, but the other is always there for backup. I've seen cars with this "power dtc" and after just replacing the relays, I've never had the code return. If one's getting old and sticky, probably a good idea to just replace them both.

 

The troubleshooting steps in the manual were usually organized with the aim of narrowing the diagnosis down to the actual culprit in a small number of steps.

That's certainly not the only way a person can approach solving a problem. Another way is to just buy and replace everything that sits in a socket; if that makes the code go away, then maybe you don't mind that you never learned what the culprit was. If you still have the code, then you proceed with other checks. This can end up being more steps overall than just following the suggested sequence in the manual.

Procedures in the manual also aren't magical, or guaranteed optimal, or anything like that. Sometimes you can look at the steps in the manual, and at the wiring diagram, and realize you've thought of a way to pin down the cause in fewer steps than the engineers came up with. If you're a lot smarter than the engineers, that might happen extra often. But for a lot of people, the troubleshooting steps in the manual will be a pretty good procedure to follow.

It's rarely necessary to trace the whole wiring. The diagram is available so nobody has to do that. It also shows how the circuit is laid out, how the different relays and fuses figure into it, and so on, so that by glancing at the diagram you can figure out what it will mean if you measure voltage X at spot Y in the circuit, which can simplify your job.

 

By "the right rear vent", do you mean the air grille at the right end of the back seat?

That's an intake for the traction battery cooling fan, which can run at variable speeds. When you can hear it, that usually means it is running at a high speed, responding to the traction battery overheating. That could indicate another, different issue with the car. It is not the same issue as the braking C1241.

 

Let's say you're on the internet looking at Prius Chat on a home PC. You unplug the PC (not a laptop). 20 minutes later you plug it back in. Are you still showing Prius Chat on the screen?

Nope, but after the computer reboots fully, you can do a bit of typing and show it how to get back to the website.

Just like your PC, the car lost it's short term memory. Once it boots up and goes through a few cycles, if it goes to that "website" again, the triangle will pop up.

 

The important tools for troubleshooting when something subtle is going on are the Repair Manual and sometimes (if something electrical is implicated) the Electrical Wiring Diagram. Both can be accessed in a number of ways as described here:

Toyota Service Information and Where To Find It | PriusChat

 

These days wiring diagrams are useful to find wiring faults and sometimes show how inputs are wired to a specific ecu and show how outputs connect to an ecu, but they really don't explain the operation or point with any real accuracy to a specific code or symptom. In fact almost no one in the US really knows the program logic that is the real circuit logic.

Like a lot of common Prius issues, the solution is often the most common repair, which in this case may be the expensive brake booster.

Firing the "cheap" parts cannon is often an owner's first choice but comes with the downside of lost time and money if and when there are no results. Those diagnostic procedures tend to reduce the collateral damage. On common issues, experienced hybrid mechanics can often diagnose the issue in minutes. Which is why I often suggest having the dealer or independent hybrid mechanic zero in on the issue first and then you can consider the alternatives with confidence.

If I were convinced power or relays were the issue, I might start with the fuses, fusible links and relays below. However I would voltage and continuity check each item first. They rarely fail especially in an intermittent way. Plus the fusible link is expensive and difficult to replace.

 

The way Toyota divides information between the Repair Manual (RM), the Electrical Wiring Diagram (EWD), and the other service documents, is explained to some degree on our wiki page:

Toyota Service Information and Where To Find It | PriusChat

Generally, the first stop for a specific code or symptom is going to be the RM. For a specific code, there will be a complete section there explaining what the code means, how the car detects the condition, how to troubleshoot what caused it, and how to confirm a repair.

The RM section usually also has its own simplified piece of the wiring diagram, one showing just enough to clarify what's going on with that code. (These RM diagram fragments even sometimes add information the full EWD doesn't show, like transistors and pullup resistors inside ECUs, etc., when that helps with understanding how the circuit works, what measurements you should expect in different conditions, and so on.)



Those simplified diagrams don't always show details like the wire colors (though I notice this example does have the letter codes for the colors shown; not all of them do), the locations and shapes of connectors, or intermediate connections along a circuit path. They just show the essentials for making sense of the circuit. When you need the rest of the details, those can all be found in the full EWD (which is in color, so it not only shows the letter codes for wire colors, it shows the colors).

For explaining operation, even the RM doesn't have the whole story. The introductions to what parts are in the system, what they're for, and how they do it, are all found in the New Car Features manual (NCF), also described on the wiki page above and available in the same ways. Those explanations can be quite thorough and include a good deal of detail. Descriptions in the RM assume you've already seen the material in the NCF, so sometimes they feel like jumping in the deep end if you haven't.

Solving most non-trivial problems using these resources will usually be a kind of active-reading exercise, where you treat the RM, NCF, and EWD not so much like things you can just read an answer in, more like three witnesses you interrogate and compare stories from, and go back and cross-examine after getting new evidence, multimeter readings or what not, from the car. When you approach them that way, you tend to notice there's a lot more useful information there than would jump out at you if you were passively reading.

 

Mentioned previously in thread:

Per the OP's earlier thread, a C1241, accompanied by C1310, C1343, C1344.
I suggested troubleshooting the C1241 first, then seeing which of the other codes return.

Also mentioned previously:
On common issues, experienced hybrid mechanics can often diagnose the issue in minutes.

From the Repair Manual for C1241:


Taking the above into consideration, maybe this isn't a bad place to start for DIYer, considering how cheap and easily accessible they are compared to pulling ecu connections apart and checking voltages:

Just off the top of my head, and anyone correct me if I'm off base, two relays supply the ABS.
I've seen cars with this "power dtc" and after just replacing the relays, I've never had the code return.

One thing I can tell you for sure, is that you can usually hear a very clear difference in how strong the ABS motor runs whether one or two relays are installed/functioning

 

maybe this isn't a bad place to start for DIYer, considering how cheap and easily accessible they are compared to pulling ecu connections apart and checking voltages

Sure, those are easily accessible, and that's the kind of thing that can even be checked by 'borrowing' one of the similar relays from something else in the car (or two of them, if you don't have the INF code telling you which one is in question). So one could still avoid spending money on a relay until it's known to be the issue.

Sometimes a conversation that starts off about the comparative attractions of looking stuff up in the manuals, or just diving in, will end up morphing into one about what procedure should then be followed (usually painted as a choice between something complicated and impractical or something sensible). So it's good to remember that looking stuff up doesn't in any way limit your choices in how you proceed with the information you found.

The manual will usually have suggested steps for troubleshooting, and you can always just follow those in order if you want. Many times, that will be a pretty good procedure. You're also perfectly free to change the order around, improve on it, or set it aside and improvise your own. You can have all kinds of reasons for that, like what's more convenient in your own situation, some other information you have that gives you a hunch, and so on. Those are all the same choices you'd have whether you checked anything in the manual or not. The advantage of checking is in being able to base those choices on more and better information, and double-check that your improvised procedure will still cover the different possibilities.

Sometimes even if I don't swap relays, I'll pull them out and use their sockets as test points for a meter; the diagram can tell me when those are equivalent to less-easily-accessible pins on ECU connectors, etc. (Equivalent if the reading is normal, anyway. If it isn't, then it's up to me to work out how changing the test location changed what that tells me.)

One thing I can tell you for sure, is that you can usually hear a very clear difference in how strong the ABS motor runs whether one or two relays are installed/functioning

The motor is powered by two other relays, ABS MTR and ABS MTR 2, which aren't the ABS NO. 1 and ABS NO. 2 relays concerned in this thread. (I get that nobody said they were, but having both sets of relays mentioned in this thread might possibly confuse someone reading along, so it's worth being clear about.) In the fusebox, ABS MTR is the big relay right next to the smaller ABS NO. 1 relay, and likewise for ABS MTR 2 and ABS NO. 2.

The ABS MTR and ABS MTR 2 relays are deliberately set up to run the pump with different strength (ABS MTR feeds through the honkin' resistor that mounts under the dash, and ABS MTR 2 feeds directly). The ABS NO. 1 and ABS NO. 2 relays are part of a different game, powering the electronics of the brake system, especially the two redundant systems in the skid ECU.

Might be a good illustration of the kind of thing that could legitimately confuse anyone, without a chance to check in the manual.