Ferrari 328 Fuel Injection ECU Testing(K-Jetronic/Lambda CIS)Carl Rose, Brian Crall, & Mark FoleyNovember 2004 v1.0

Tools Required: 10mm combination wrench Digital Multimeter with ohm, AC, DC capabilities Jumper bridge (see picture)

First, determine the “zero” point for your individual multimeter (ex: mine reads0.7ohms at rest):

The K-Jetronic ECU is located in the passenger (RH) rear compartment. Unzipthe cover & remove the velcro antenna cover:

Slide the carpet cover plate & remove underlayment to reveal the ECU mountingplate:

Remove the three 10mm screws (each with lock & flat washer). My car did nothave a screw located in the right top (RUO) quadrant:

Pivot the plate out, turning over to expose wiring and ECU:

Remove the main ECU multi-terminal connector. Remove the small screw on topand slide the round cover off to expose wiring:

Terminal #s are clearly marked on the connector. Many positions areunoccupied:

Start testing as per the workshop manual for F105C040 motor:

Key off, ECU disconnected.

Coolant temperature NTC switch (on expansion tank): bridge terminals 5& 7. Resistance should be virtually zero below 54 C and infinite above 54C

COLD

HOT

TPS switch idle contact: remove the diode for cold start injector & insertjumper (see fused jumper I made up in picture). Resistance should bevirtually zero at idle and about 2000 ohms off-idle:

Leave the jumper in place. Bridge terminals 5 & 12 and open TPScompletely; when cold resistance will read zero but when oil hot shouldread infinite and become zero as throttle plate opens > 60 degrees:

Oxygen sensor internal resistance is measured by bridging terminals 4 &2; cold this will be infinite dropping to 300-1500ohms when warm (picturetested immediately after shut-off):

Testing ECU grounds: connect in turn terminal 5 to ground & then terminal16 to ground. Each should read 0.2ohms or less:

Remove the connector plug to the blue fuel injection safety switch at thefuel distributor. Turn the key to “run” (but not “start”). Set meter to DC volts& bridge terminal 5 (-) & 8 (+). Reading should be 8-13v to measure inputvoltage from protection relay to ECU:

Turn off ignition key. Reconnect the fuel injection safety switch & cold startdiode. Plug the ECU terminal into the ECU; there is a nifty factoryinterconnector tool but is not required. Start engine & allow to warm. Setmeter to AC and bridge terminal 15 (-) and terminal 8 (+). Expect to see7.4v dropping on cold start to 6.4v as engine warms dropping to 5.3-6.3v(+/- 0.15v) to signify closed loop operation when hot:

COLD start

HOT with oxygen sensor connected:

HOT with oxygen sensor disconnected:

Measuring run voltage at oxygen sensor: on DC setting, bridge terminals 2 (-) lead & 4(+) lead) and look for voltage 0.1-0.8v:

Notes:

Disconnecting frequency valve while running shows no effect (although it isbuzzing when connected). Resistance across the terminals is 3.1ohms.

Measuring duty cycle of frequency valve (from terminal 15 blue/yellow (+) leadwith (-) lead to ground) shows about 11-14%. Even with oxygen sensordisconnected, DC measures 23%. I’m not certain if this is the proper method tomeasure?

To summarize abnormal values:

Coolant temp switch reading at ECU not infinite when cold. Directly testingswitch does show infinite resistance. Disconnecting input plug to ECU/relay platedemonstrates no continuity between purple wire & ground (i.e. no obvious short).

TPS switch “full throttle” position when warm doesn’t seem to be functioning. Oxygen sensor – when immediately shut off – isn’t registering low resistance at

ECU. AC voltage from ECU for duty cycle settings is very low, both at cold start and

hot. Wide-open throttle enrichment shows low voltage value (2.2v instead of 7.4v).

Oxygen sensor DC voltage fluctuated from 0.796-0.804v at idle.