Volvo: B230F stuck in limp home mode, plugs and sockets, earth connections

Question
My Volvo 240 is a 1990 UK spec 2.3GL estate with B230F engine controlled by Bosch 0 227 400 169 ignition control unit and Bosch 0 280 000 561 fuel injection control unit.

It was fine one day.  Next morning it was in limp home mode (2000 rpm max)with warning light on from the start.

The ignition diagnostic (from pin 6) said the TPS was faulty.  The fuel diagnostic (from pin 2) wouldn't work.

I removed and checked the TPS and it was indeed faulty, but after filling it with switch cleaner and turning it back and forth a few times it was fine.  I replaced and adjusted the TPS and reset the ignition control unit.  The ignition diagnostic now read 1-1-1 and the ignition test mode confirmed that the TPS was now working.  But pin 2 still gave no diagnostics.  The engine continued to run only in limp home mode.  I have checked that there is continuity all the way from pin 2 in the diagnostic unit back to the plug on the fuel injection control unit and the other connections are shared with the ignition control unit, but no way can I get any fuel diagnostics.  I've cleaned and checked all the connections to the control units and the sensors and the intermediate plugs and sockets and earth connections, but all to no avail.

I figured that although the fuel injection control unit wouldn't talk to me, it maybe just needed resetting so I left the battery disconnected over night, but still the engine is stuck in limp home mode.

I'd really appreciate any ideas!

Thanks for your help.

Answer
Geoff,
Hook up the VST (Volvo scan tool)directly to the control unit via the piggy back connector, that way you can look at the values that are input and see what values look to be "out of spec". If no scan tool find someone that has one or try a know good control unit for starters. You might also if not done already look and make sure that all compontants are plugged in and tight.