Use of Memory Clear and Diag Check for ECU Errors instead of MUT/OBD


November last year was a thread on "Code Reader" about MUT and OBD etc.

In the middle of it reference was made to "Memory Clear" and "Diag Check" wires for rudimentary reading of two digit ECU error codes through flashing dash warning light, and how to reset.

I can find some reference in my service manual (2005 FG/E) but the description is a bit shorthand and I'm loathe to experiment. Can anyone enlighten me on the procedures and what to expect?

This is related to my request for an owner manual, but this won't be found there. Apologies if that confuses. I couldn't change the title of previous topic and still need a manual.


Kodiak Buckaroo
I replied to your email, but I'll also post the infomation here.

Sorry to hear of your troubles :(
But WOW, Kirgyzstan ! :Wow1:
Below are two PDF links

They ares, one if you have the MUT-II (I'm guessing you don't) and one using the 'flash codes'.
The plugs(that act as 'switches') are on the passenger side, under the flip down panel which has the windshield washer fluid tank.
Mine is a LHD and 2002 so your location might be different.
There are here :

Please let me know if I can be of any more help



magic thanks Mark, very much appreciated,

dark here now, I'll hopefully read the past error code with the flashing light in the morning.


so far worked as advertised. The two wires are directly to the Bosch Pump ECU, by-passing all the non-standard Mitsubishi MUT stuff. Only error codes though, no measurements. For those looking for a way of monitoring it looks like its possible to build a wiring harness to get from the engine ECU to something that reads the Bosch protocol. A brief google suggests its been done. Later models than mine (2005) have other computers hooked into the MUT/OBD system.

Anyway, no current errors, here's the past error codes in the order in which they occurred (reverse of order in which read):-

45 - Reverse Engine Operation
16 - Accelerator Pedal Position Sensor II
32 - Boost Pressure Sensor (sets boost pressure to 0)
24 - Accelerator Pedal Position Sensor I
14 - Back up Engine Speed Sensor
15 - Engine Speed Sensor

Each of the above would turn the orange engine warning light on.
16 + 24 (both accelerator pedal position sensors) would turn red warning light on, back up driving ok
14 + 15 (both engine speed sensors are faulty on start up) would turn red warning light on, = undrivable

Sadly there is no time associated with when the past error codes occurred. I have no way of knowing what occurred concurrently. I also don't know if the unit only stores the last 5 error codes or .... how many?

The boost pressure I can perhaps understand due to the altitude. I've since cleared dust from the air filter (6 weeks old but conditions dusty). I can also conceive of dust around accelerator pedal sensors and will investigate. I can imagine accelerator pedal sensors leading to engine speed varying. The effect of changing fuel tanks may be a furphy, then again fuel feed may explain engine speed sensor error. Difficult to know though, and it all went back to normal (no current error code) when I descended.

Any more scenario suggestions welcome.

Last silly question. Does boost pressure measure differential pressure (to atmosphere) or absolute pressure? I suspect differential as the unit sets it to 0 kPa on error. Does anyone know?


The two wires (Memory and Diag) come directly from the engine ECU. Not much use for Owen and others with later models and MUTIII but the "OBD" connector next to those two wires that has only one wire connected to it (on mine) is likely the K-Line connection from the engine ECU. K-Line was pre CAN Bus. Its been re-labeled by Mitsubishi in the length of a meter of wire to MUTII. Chances are there's a relatively easy way of reading it - but it will have to wait until I'm back in Aus. So far service manual schematic, circuit diagram and vehicle are consistent.

Meanwhile, back to the mundane of cleaning the boost pressure sensor today. Every little helps!


Boost pressure sensor very clean!

One last bit of very important information .... the 16 pin OBDII connector that only has one wire has it connected to pin 7.

That's the K-Line pin, the one that carries the data. All that's needed is a 12v to pin 16 (used to indicate there's power to the ECU) and an earth to pin 5.

I suspect the 12v and earth appear in the second, related, Mitsubishi MUTII connector. Some pictures have MUT connection using both connectors. Haven't found the MUTII connector on the circuit diagrams yet.

Given the above one of the generic OBDII to USB cables "should" work. Along with any of the PC software varieties that will read K-Line (most).

One small step!

No use for later models that have MUTIII and more than one ECU (things like transmission and central locking and air bags).

Realistically it will wait until I get back to Aus in about 6 months. But if the red light comes on too often I might have to bring that forward!


Photographer, traveller
K-Line is a slow-speed open-drain bi-directional bus, IIRC a connection starts at just 5bps then ups to a higher speed (variable and max 10kbps) once an address is accepted by the ECU. But if there are USB dongles that handle all that so much the better.


I've been doing some reading .... Elm327 (genuine not cloned) looks promising. Its a PIC based protocol converter. OBDII one side, RS232 (USB) t'other side.

OBD-II Protocols supported:
--ISO15765-4 (CAN)
--ISO14230-4 (KWP2000)
--J1850 VPW
--J1850 PWM

K-Line is the ISO14230. Yes, its slow to start then speed increases. There's a "keep alive" command.

Now I just have to climb in the cab and figure out which of the wires to the other connector for 12v and ground need moving to the OBD connector! A bit of confusion between OBD and Mitsubishi's Multi-Use Tester.

I'll probably have it sent to Lhasa.
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Kodiak Buckaroo
I like the sounds of this (that only one wire is needed for data). It sounds like perhaps we could have a working OBD-II port with the additon of a power and ground?
Am I reading/thinking that 'right' or am I just too hopeful and hearing what I want to hear?
I run Scangauges ( ) on all of my vehicles (except the Fuso of course) and they are awesome. Not only all the data from the computer (speed, temp, volt, throttle postion, timing, etc, etc) but trip data for current, day, etc and the ablity to read and clear codes on the fly (my XC90 is a code throwing mother).
I'll contact scangauge and see if I can get some input from them with the above info.
Thanks a bunch for the information . . and doing it in Kirgyzstan :Wow1:


you are reading it correctly Mark.

And it just got better. One more piece of the jigsaw.

At the bottom of page 13E-16 of the troubleshooting document you provided, and I have same in the manual for my 4D34 engine, is the following description of connecting the MUT tester:-

Place the starter switch at the LOCK position.
• Connect the a Multi-Use Tester II harness to b Multi-Use Tester II
and insert the c read-only memory in the tester.
• Connect the connector A to the cigar lighter socket.
• Connect the Multi-Use Tester II connector C (16 pins) to the data link
connector B (16 pins).

The data link connector is the 16 pin OBD connector with only one wire. I now believe the cigarette lighter connection provides the earth and 12v I've been missing.

I'd been mistakenly assuming that all four connectors of the MUT tester connection (pictured as special tool MK327601 in that document) had to be connected and misled by another empty socket near our two wires for blink codes. Durrrrrr.

So a little bit of rewiring of the 16 pin socket on the vehicle, or make up a cable with a 16 pin female OBD2 connector out and 16 pin male to vehicle female plus cigarette lighter male. We need to end up with 16-pin female OBD with pn 7 our single K-line data wire, pin 5 ground from cigarette lighter or elsewhere, pin 16 12v. My connector has that single wire already at pin 7.

The protocol is K-line, which is ISO 14230-4 KWP, which is one of the OBD2 protocols. Pre CAN Bus.

I believe an Elm327 cable (OBD2 to USB protocol converter) will then let us read the engine ECU. Same as in Pugslyyy's current thread using the bluetooth version.

Reading the Scangauge web page it looks like Scangauge will connect to our modified OBD2 socket, and recognises the same protocols as Elm327. I haven't found a fuel pressure sensor so complete trip data may not be possible.

Its easier for us than Pugslyyy and Owen. If the standard codes don't match we have the two digit PIDs for error codes, data and actuators. We also have the formulae for the data. We probably will even be able to test the exhaust brake without getting out of bed (someone had a problem with that a couple of weeks ago).

This could be really expensive though ..... maybe as much as $20 ... :) I'm kicking myself for not looking harder a couple of years ago.

Has to be worth a try ..... but a bit of caution. Some of the Elm327 cables are Chinese clones which may not function as expected.

Sorry if that's too much info, it seems to help when I write it down. Getting clearer every time.

Simply - add ground and 12v to our connector, buy an Elm327 cable, load the software to whatever, or add the ground and 12v then plug in Scangauge. Bob's your uncle!

Easier than finding Gin Gin?
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just been up to 4,988 m. About 16,350 ft.

Only error message was 32 "Turbo Boost Pressure". Which makes sense.

The road in China is sealed and not too steep so third or even fourth gear a lot of the way. Very different to Kirgyzstan which was a track, steep in places, difficult to gather momentum.

On ascent if I kept the revs above about 1800 rpm then light would stay off most of the time. Descent it was stubbornly on until a little below 4,000 m and a little acceleration.

The red light that was potentially a major problem a few days ago has now been relegated to something which is understood and predictable.

Hopefully there'll be an OBD cable and a couple of other bits (like a transfer case front oil seal) waiting for me in Lhasa.


4988 m isn't 5,000 m is it. :) :)

I tried inflating the tyres, making little piles of rocks, and putting the gps on the roof, but it just wasn't enough.

I climbed a little 13 m hillock to take a photo. :) :) Beautiful and stark.

Camped at 4,200m so starting engine may be interesting. I think today's pass is about 5,200 m. In a couple of weeks we'll camp at 5,200 m (Everest Base Camp).

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