Hi I own a UK 300e-24V 1991 W124. The chassis no is 124.031 and has the USA 300ce 24v (124.051) 104.980 3 litre 24v engine with CIS Ke or CFI fuel injection.

On checking my engine fault codes, I discovered using Socket 3 (Data Link Connector 16-pin), that I had fault code 9 – “Current to EHA is Illogical”

This was the only fault present and cleared it using the known techniques. I the drove the car and the fault code 9 reappeared. I the disconnected the 55-pin connector from the CIS-E unit and performed a continuity measurement between pins 55 and37 and the value read 19.7ohm. Great I thought, the cable harness from CIS-E to EHA is correct and the basic resistance of the EHA is in tolerance.

On connecting the DVM in series with the EHA, with ignition on engine off, the EHA only drew 11.4 mA - ( I thought it should have been 20mA). On start up the current rose to about 20mA. It only went negative with deceleration fuel cut off, dipping to about -30mA and then returning back to 11mA.

The engine starts fine and drives without fault apart from a poorer fuel consumption and poorer performance, than when I first owned the car. I have had the car nearly two years. I had to replace the MAS control unit for Dealer replacement and the part number of the new one supersedes my old one. When I then took it for its annual emissions check, it failed and was running at about 3.0%. It was then corrected and this year it passed at 1.0%

1) My problem is there is no catalytic converter fitted to my vehicle nor is there a 02 sensor (lambda) and hence my system is an open loop system so why does it need an EHA to correct for rich or lean?

2) Can any one tell me what the current measurements should be for a UK spec 104 and why does it need an EHA any way?

3) what causes incorrect current readings at the EHA on my system anyway?

Any help would be very much welcome.

Thanks

Tony