BMW Bosch Motronic 1.3 DME/ECU: Wiring Diagram + Chip Layout

Diagrams showing the internal wiring structure of the Bosch 1.3 DME electronic control unit for injected BMWs that use it, E30, E28, E34, etc...

High quality PDF - HERE.

Bosch Motronic 1.1-1.3 DME Complete Guide - HERE.

Bosch Motronic Plug Connector Pinouts - HERE.

E30 318i: Speedometer / Odometer faults + check list

If your E30 speedometer is broken, your odometer isn't turning or both, then here is a troubleshoot check list to find and fix the fault. Doing the work yourself is a bit fiddly, but totally doable if you are handy with a soldering-iron.

** A more detailed guide / thread all about E30 speedometer / odometer faults by 03IRM3 on r3vLimited.com is here - https://www.r3vlimited.com/board/forum/e30-technical-forums/general-technical/59019-e30-speedometer-repairs-failure-modes, which was a great help. **

NOTE: If your speedometer is not reading, before starting to diagnose the instrument the first thing to check should be if there is a pulse being generated by the speed-sensor in the differential, see E30Zone Wiki here.

Broken Odometer drive gear.

This is the most common problem when the odometer has stopped turning. The drive gear from the stepper motor that turns the larger cogs tends to split on higher mileage cars causing it to skip teeth and not turn the odometer gearing. Replacement gear sets can be bought from eBay for a few quid.

Burnt out resistor.

This is the main power resistor on the 12v + input to the PCB and it's never usually failure of this component that causes it to burn out. Instead, failure of a component further upstream is usually the culprit by drawing way too much current, causing the resistor to work double-time and overheat. This one was still working amazingly, given the heat it had been producing that charred everything around it, but I threw a new one in anyway. The value was about 150 ohms, so that's what I went with.

Blown capacitor.

Sudden failure of both speedo and odometer can often be down to the main power capacitor blowing. This is visible in the above pic to the right of (and next in sequence to) the burnt out resistor. It's a basic 220uF electrolytic capacitor and is very simple to replace with only two pins needing de-soldering, so should be the first step in troubleshooting a dead unit, even if the cap itself doesn't appear blown. Mine had been scorched by the overheating resistor, but seemed ok. I replaced it anyway, but it did not help with mine.

Snapped wire on Odometer stepper-motor coil.

This is rare, but does happen as 03IRM3 has seen one and mine had this too so I guess it does happen, where one of the single strands of copper coil for the stepper-motor snaps off its pin on the PCB. It’s possible that this happens due to time/age and vibration in the vehicle, but could likely be due to manhandling the unit while it is out for other repair work. Either way, it’s an easy fix to just solder it back in place and will be stronger than it was before at least.

UAF chip blown.

If none of the above fixes have worked and both speedo and odo are still not working, the likely culprit is that the UAF I/C chip has malfunctioned and is not processing inputs and outputs correctly, which leads to the resistor burning out, caps blowing and the odometer coil overheating. These UAF2115 chips are common, used in many speedo/odo units, taxi-meters, tachographs etc., so replacements can be found on eBay or electronic component sites for a few £/$, but this is probably the most advanced fix needed for these units and the question at this point is whether it's worthwhile. 03IRM3 has replaced chips as a last resort only to find the unit still won't work, so I decided that with all other fixes not working and my odometer still needing new drive gears that it was time to junk it and seek a replacement unit... [THIS POST].

E39 530d: Engine Tuning thoughts...

I've no intention of fiddling with the engine any time soon, but a work colleague has recently had his 320d chipped by Peco, a small firm in nearby Birkenhead, Wirral, who you probably know best for their exhausts and it's food for thought. The chip costs £300 and my colleague claims that the car feels much quicker, without having a noticeable effect on economy.

Hmm, sounds too good to be true really and it would be a shame to stifle the 5's superb fuel consumption, but if I do decide to up the power of the 184bhp diesel in future it seems that the chip is where to start so I'll be asking Peco soon about their 530d module.

If the mood takes me though I'd love to try out a couple more subtle mods to make sure power goes way past the 200bhp mark. A K&N panel air-filter for starters. I don't fancy a full on induction-kit, it's not a Scooby after all. Then for the main course installing a larger intercooler further forward in the bumper. The OEM i/c is very small, so it wouldn't take much to find one a bit larger, a Ford Transit i/c would be an ideal donor to fit into the front-bumper, then fab up custom extensions for the pipes. With the chip installed and mapped-in after this lot we should see a nice power gain.

Watch this space.