pcm/fan question

Reply Subscribe

Thread Tools

Search this Thread

Nov 3, 2009 | 03:12 PM

2manyToyz

Thread Starter

Registered User

Joined: Jul 2008

Posts: 72

From: Upstate ny

pcm/fan question

fans were not working and so i ended up tracing to a bad relay(s) by dropping in known good ones (after testing fan function and swapping temp sensor)

my question is what is the feedback mechanism for the pcm to recognize that the fans are or are not working and if it does see that fans are inoperable what kind of other electronic functions get screwed up as a result?

Nov 3, 2009 | 03:15 PM

bw_hunter

Registered User

Joined: Jul 2002

Posts: 1,942

From: Kissimmee, Fl, USA

Quote:

Originally Posted by 2manyToyz

I don't believe there is any feedback loop as you describe. The PCM commands the fans on and 'assumes' they're on. Nothing else should be affected.....

Nov 3, 2009 | 03:27 PM

97FormulaWS-6

Registered User

Joined: Mar 2001

Posts: 2,667

From: SLC, UT

Yea, there is no "feedback" for the PCM to the fans. It just supplys the trigger voltage to the relay; that's it.

Nov 3, 2009 | 03:57 PM

shoebox

Registered User

Joined: Dec 1969

Posts: 27,728

From: Little Rock, AR

There actually is feedback info, but it is just from the PCM to the relays (DTC 77 for OBD-I and DTCs P1641 and P1642 for OBD-II). The PCM monitors those circuits for inappropriate electrical signatures (opens or shorts) .

There are no other consequences of the fans not working, except for the possiblity of higher than normal engine temps.