I'll try the RPM sensor swap in the AM.
Jarrod,

You might also try testing the RPM sensor in EZK Mode 2 for a 1-4-1 (OK) code. See Bentley 280-4 item 4.

I've never had a "known bad" one, but the originals I replaced on '93 240 and 940 were really ratty-looking down by the sender. Worth replacing, IMO.

As for the LH mode 2 test, I believe what Bentley 241-7 item 8 refers to is NOT the RPM sender, but the "Engine speed signal from the ignition system". I don't have any LH green books, but that's how it's decribed in my Regina manual, where it says a 3-3-1 means that signal is OK.

So far I can't find where it addresses "NOT OK", but I think that "speed signal" is the basic timing pulse to LH ECU pin 1, without which the pumps won't even run (except for the Key On buzz). So it would have to be OK (3-3-1) on a running engine (???).

I dont believe the LH 2.4 ECU gets any direct input from the RPM sender, so it relies on the "speed signal" from the EZK CU, which does get the RPM sender input.


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Bruce Young
'93 940-NA (current) — 240s (one V8) — 140s — 122s — since '63.