P1689 Control Unit Faulty
 

Has anyone seen a P1689 error code? My friend has a 97 Boxster with CEL, so we connected to my Durametric and here is what displayed:

P1126 O2 Sensor (4-6)
P1124 O2 Sensor (1-3)
P0102 Mass Air Flow Sensor Short Circuit/Open Circuit
P1689 Control Unit Faulty

The motor is running great with 60,000 miles on the clock. I did a search on this forum with this error code but not much found for this alarm.
Thanks

Edit... I will add that the voltage on the pre-catalytic converter O2 sensors are flat on both banks (0 volts)

Jager, my Service manual says P1689 Engine control module faulty. If such faults occur, replace the ECM. No more info in the oem manual. :confused:

I guess I would start by seeing if there is voltage in the harness going to the O2 sensors. If not, it could be the ECU is dead. Is there a fuse or relay for the ECU? What do the voltage graphs look like for the sensors, before and after cats? The befores should look like a sine wave and the afters should be pretty close to a straight line.

Then, I would swap out the MAF with a known one to see if its good. There are also a couple of diagnostics for the MAF on the duramteric, voltage, I believe and maybe resistance.

Do the MAF values vary at all upon acceleration?