Category: Servicing and Setup
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ECU Diagnostics – part 13.3 : MBE-ISOTP
SUMMARY We now understand the communications protocol used by Easimap (the Windows software supplied by the ECU manufacturer) and can use it to ask the ECU for whatever data the car has to offer. We can then manipulate the responses we get back from the car and format them to make sense to us. TL;DR…
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ECU Diagnostics – part 13.2 : OBD-II
The OBD-II diagnostic protocol is well defined and information about it can be found in On-board Diagnostics. It’s a mish-mash of many diffrerent standards, both physical and electrical, that I’ll refer to as OBD-II. There’s also a complete breakdown of the Services and PIDs (see below) that can be found in On-board Diagnostic PIDs. I’ll talk…
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ECU Diagnostics – part 13.1 : MBE-Broadcast
The simplest of the three Caterham OBD port diagnostic protocols we know about is what I’ve called MBE-Broadcast. As soon as the car is put into ignition switch position 2, the ECU starts to spit out a this stream of data on the CAN bus. Unlike the OBD-II protocol and the MBE-ISOTP protocol, this a…
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ECU Diagnostics – part 13 : Three Diagnostic Protocols in the MBE 9A4 ECU
This one’s just a short post to introduce the next three posts. In our investigations of the MBE 9A4 ECU we’ve found three different diagnostics protocols supported on the OBD port. The following three posts will summarise what we’ve learnt about each protocol and will be updated with new information as it becomes available. 13.1…
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ECU Diagnostics – part 12 : OSI 7 Layers for Caterham Diagnostics
Communications protocols are often called protocol stacks… they’re layers, or stacks, of different protocols… one layered on top of the other from lowest level (hardware/physical) to highest level (software application). This is where the OSI 7 Layer model comes in… it standardises how we think about the layers and allows us to talk about where…
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ECU Diagnostics – part 11 : Logic Analyzer on the CAN Bus
To test out my theories and the code I’d been writing, I needed a simple test and a way to make sure the code (and I) was doing what I thought it should be. The code part was easy, take the JSON files I’d created from the Easimap EC2 file and use it to ask…
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ECU Diagnostics – part 10 : Decoding EC2 Files
Now we need to start proving some of our theories about how Easimap is actually talking to the ECU. And it seemed to me that if I was going to prove anything then I’d need to pass a lot of data through any theory I came up with, and that meant writing a program –…
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ECU Diagnostics – part 9 : The Easimap Protocol Theory
Ok. so we’ve set ourselves up to be able to look at what is going on with a Caterham diagnostics port, we’ve talked a bit about the theory of what we might see from the port and we’ve also seen that Easimap talks to the ECU using a higher level protocol called ISO 15765-2 (ISOTP).…
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ECU Diagnostics – part 8 : Easimap uses ISOTP (sort of)
Ok, that’s enough of the theory about mapping. Lets get back to what Easimap is doing when it talks to the car. When we left this subject last we had got to the point where we could see what Easimap was sending and receiving on the CAN bus, but we didn’t know what it meant.…
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ECU Diagnostics – part 7 : ECU Maps and Mapping
People often talk about “mapping” a car. When they do that they’re usually interested in one or more of three things: To increase its performance Improve its fuel economy Improve its drivability So what is mapping? In technical terms a map is a translation, or conversion, function that takes an input and produces an output.…