Trouble codes parsing array index why start with 1

[JRJian]

NSRange codeRange = NSMakeRange(1, bytes.count-1); NSArray<NSNumber*>* codeBytes = [bytes subarrayWithRange:codeRange];

The returned result is different from other OBD apps.（Such as Auto Doctor、ELM327...）

If I change the index to 0，the result will be consistent.

[mickeyl]

Let me show you an example, here's communication over protocol 7:

I ask for 03 and get the following rawResponse:

(lldb) po self.rawResponse
<__NSArrayM 0x28150cbd0>(
18DAF110100A430401100148,
18DAF1102101700210000000
)

Stripping the ECU IDs and reassembling the fragments gives me the following cookedResponse:

(lldb) po self.cookedResponse
{
    10 =     (
        4,
        1,
        16,
        1,
        72,
        1,
        112,
        2,
        16,
        0,
        0,
        0
    );
}

We are seeing ECU #10 responding with 12 bytes. To my knowledge, every DTC is encoded as 2 bytes and the first byte of the whole response to 03 and 07 is the actual number of encountered DTCs, i.e. in this example we are seeing 4 DTCs where as the actual values are P0110, P0148, P0170, and P0210.

If you think this is wrong, could you show me example data from your car?

[mukulpandey57]

Hello @mickeyl , I am getting "P2800" from this Library, but other apps or wired scanner reads "P1628". Please suggest or If I'll change the index to 0 will fix it as above mentioned by @JRJian In NSRange codeRange = NSMakeRange(1, bytes.count-1); NSArray<NSNumber> codeBytes = [bytes subarrayWithRange:codeRange]; screen shot of wired scanner.( what is mod $12 i don't familiar with)

[mukulpandey57]

NSRange codeRange = NSMakeRange(1, bytes.count-1); NSArray<NSNumber> codeBytes = [bytes subarrayWithRange:codeRange];

@JRJian @thdankert @mickeyl , is this code correct or have to change the RangeIndex to 0? Please Help. (Not getting ABS fault codes specifically "U0102" )

[mickeyl]

Thanks for opening this issue, I think you are up to something. My implementation of the DTC parsing code is based on SAE J1979_201408, which is the reference, but I may have mixed up some of the tables depicted in there (granted, it's quite a confusing spec in some places). I have developed the DTC-implementation against an OBD2 Simulator (since I do not possess so many cars with actual failures), it might be possible that this Simulator has a broken implementation of the DTC answer. I will double check with the spec later this week and report ASAP.

[mickeyl]

I may have spoken too soon. Upon my inquiry, the simulator developer just got back to me and claims that for all CAN-protocols, the answer to 03 has to report the number of DTCs before the actual codes. For all other protocols, this number will be omitted.

Can anyone confirm or deny that?

[mickeyl]

See also the accepted answer to https://mechanics.stackexchange.com/questions/51226/obd2-mode-3-wrong-response – I trust these folks, as they have a lot of experience in seeing "real world" values.