98eldocoupe Posted April 27, 2008 Report Share Posted April 27, 2008 1998 Eldorado w/ 68,000 miles, several months ago got a "Service Engine Soon" light with the code of DTC P1660-Cooling Fan Control Circuits . Cleared several times and it always came back. Mechanic (new to this car as Caddy dealership closed down) found one fan's bearings was faulty (motor grinding) and he decided to replace both accessory fans and the one of the 3 relays tested bad. Warning light returned, same code, then they replaced the additional 2 relays. I was told one fan goes on when the radiator temp hits a certain level, the 2nd goes on when additonal cooling is needed and also for use with the defrosters. After repair, "Service Engine Soon" again, same code, mechanic thinks it's a bad wire in the harness. Tried to trace it out and wiring seem to be OK, now states that he tested the "Body Control Module" (BCM) which is at fault. Wants to replace this. Other issues I have noticed during the past 6 mths maybe related maybe not, driver's window sometimes does not work, up or down, "Serv Stab. SYS" light comes on with a code of TCS C1287 & TCS C1288 Steering Sensor Rate Malfunction/Steering Sensor Circuit Malfunction puts into history (steering sensor was replace once in 1994 under warranty). Now before I OK the replacement of the BCM which I hope will solve this problem, is there anything else that needs to be checked first, it just seems they are chasing the problem down, step by step and perhaps not looking at the overall and addressing the real problem if there is one? Link to comment Share on other sites More sharing options...
adallak Posted April 27, 2008 Report Share Posted April 27, 2008 When you have several electrical problems it never hurts to check the battery contacts and cables for corrosion and tightness. The saddest thing in life is wasted talent Link to comment Share on other sites More sharing options...
WarrenJ Posted April 27, 2008 Report Share Posted April 27, 2008 The BCM isn't even mentioned in the Circuit Description or Troubleshooting document (see attached). Oddball electrical problems, on rare occasions, have been traced to poor connections on the underside of the engine compartment fuse block. Yeah . . . a long shot, I know. Regards, Warren P1660.pdf There is no means of avoiding the final collapse of a boom brought about by credit expansion. The alternative is only whether the crisis should come sooner as the result of a voluntary abandonment of further credit expansion, or later as a final and total catastrophe of the currency system involved. - Ludwig von Mises Link to comment Share on other sites More sharing options...
98eldocoupe Posted April 27, 2008 Author Report Share Posted April 27, 2008 The BCM isn't even mentioned in the Circuit Description or Troubleshooting document (see attached). Oddball electrical problems, on rare occasions, have been traced to poor connections on the underside of the engine compartment fuse block. Yeah . . . a long shot, I know. Regards, Warren Perhaps he meant PCM but mispoke and said BCM?? I've been reading that these accessory fans go on "LO" when temp reaches 224 degrees and "HI" when coolant temp reaches 229 degrees (Other posts state they turn on when temp reaches 228 and off when back down to 217) Another question is that I've also read that they BOTH should be ON constantly when the AC is turned ON. When I test this out, only one, the pass. side fans turns on, then it cyles off-on-off-on, the other fan does not seem to turn on. Only did this test in a parked position, have not driven it yet to see if both fans come on or not. But is it true that they should BOTH come on, same time with AC on? Link to comment Share on other sites More sharing options...
WarrenJ Posted April 27, 2008 Report Share Posted April 27, 2008 The BCM isn't even mentioned in the Circuit Description or Troubleshooting document (see attached). Oddball electrical problems, on rare occasions, have been traced to poor connections on the underside of the engine compartment fuse block. Yeah . . . a long shot, I know. Regards, Warren Perhaps he meant PCM but mispoke and said BCM?? I've been reading that these accessory fans go on "LO" when temp reaches 224 degrees and "HI" when coolant temp reaches 229 degrees (Other posts state they turn on when temp reaches 228 and off when back down to 217) Another question is that I've also read that they BOTH should be ON constantly when the AC is turned ON. When I test this out, only one, the pass. side fans turns on, then it cyles off-on-off-on, the other fan does not seem to turn on. Only did this test in a parked position, have not driven it yet to see if both fans come on or not. But is it true that they should BOTH come on, same time with AC on? This should answer your questions. Regards, Warren EDIT: It could never hurt to remove and clean the PCM electrical connectors (Disconnect the battery first, or course). FanDescription.pdf There is no means of avoiding the final collapse of a boom brought about by credit expansion. The alternative is only whether the crisis should come sooner as the result of a voluntary abandonment of further credit expansion, or later as a final and total catastrophe of the currency system involved. - Ludwig von Mises Link to comment Share on other sites More sharing options...
winterset Posted April 28, 2008 Report Share Posted April 28, 2008 I agree with Warren, with the exception that I don't think it's a long shot, but more that it's more likely a cause for a 10 - 11 year old car. Tracing what the problems share in common will help you diagnose this - (ie fuse block, connectors). it's Typical sometimes of mechanics to start swapping out $$ parts first. After you check the underside of the fuse panels etc, check some of the connectors, and clean if necessary. I'm not sure if there is a cleaner made specifically for cleaning, coating connectors, I've been using wd-40 for many years on all my car's external electrical connectors with no ill effects. Link to comment Share on other sites More sharing options...
WarrenJ Posted April 28, 2008 Report Share Posted April 28, 2008 I've been using wd-40 for many years on all my car's external electrical connectors with no ill effects. WD-40 and Duct Tape, the two Antipodes of the known Universe. There is no means of avoiding the final collapse of a boom brought about by credit expansion. The alternative is only whether the crisis should come sooner as the result of a voluntary abandonment of further credit expansion, or later as a final and total catastrophe of the currency system involved. - Ludwig von Mises Link to comment Share on other sites More sharing options...
Cadillac Jim Posted April 28, 2008 Report Share Posted April 28, 2008 With the A/C on and the engine at idle, and under 230 F coolant temperature, both fans should be on low speed, and not cycle on an off. This is my understanding of the 1997 FSM and my interpretation of WarrenJ's posed pages from the 1998 FSM. If both fans don't come on, it's a wiring problem or one of the fans because they are electrically hooked in series for the low speed. This cannot be the PCM. I would get that fixed first, before I address the other observed issue, cycling on and off, which could be due to a perfectly good PCM seeing that the fan circuits are not working properly, throwing a code, shutting them off, and trying again. The mechanic clearly isn't checking the car before giving it back to you. This is a big no-no for dealer work. That right there would have me looking for a dealer, or a better dealer. -- Click Here for CaddyInfo page on "How To" Read Your OBD Codes-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data -- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC Yes, I was Jims_97_ETC before I changed cars. Link to comment Share on other sites More sharing options...
craejensen Posted November 27, 2008 Report Share Posted November 27, 2008 Hello! I have this same problem.. neither fans kick on and i only have a code of P1660?? Help!! With the A/C on and the engine at idle, and under 230 F coolant temperature, both fans should be on low speed, and not cycle on an off. This is my understanding of the 1997 FSM and my interpretation of WarrenJ's posed pages from the 1998 FSM. If both fans don't come on, it's a wiring problem or one of the fans because they are electrically hooked in series for the low speed. This cannot be the PCM. I would get that fixed first, before I address the other observed issue, cycling on and off, which could be due to a perfectly good PCM seeing that the fan circuits are not working properly, throwing a code, shutting them off, and trying again. The mechanic clearly isn't checking the car before giving it back to you. This is a big no-no for dealer work. That right there would have me looking for a dealer, or a better dealer. Link to comment Share on other sites More sharing options...
Cadillac Jim Posted November 27, 2008 Report Share Posted November 27, 2008 P1660 Cooling Fan Control Circuits Check the cooling fans; with the car off and engine cold, make sure that they both turn freely. Then, check the cooling fan wiring, relays and fuses. -- Click Here for CaddyInfo page on "How To" Read Your OBD Codes-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data -- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC Yes, I was Jims_97_ETC before I changed cars. Link to comment Share on other sites More sharing options...
craejensen Posted November 30, 2008 Report Share Posted November 30, 2008 P1660 Cooling Fan Control Circuits Check the cooling fans; with the car off and engine cold, make sure that they both turn freely. Then, check the cooling fan wiring, relays and fuses. Okay.. we did check the fans and they do turn freely and then the A/C Comp fuse blows all the time. So we got a new A/C Comp Relay because that was bad too and when we put that relay in then the fans kicked on.. but then it blew again.. ?? So now i'm stuck there ... could you emal me at craejensen@hotmail.com? That would be the best? Thank You very much! Talk to you later! Link to comment Share on other sites More sharing options...
Cadillac Jim Posted November 30, 2008 Report Share Posted November 30, 2008 It looks like you have a short in the AC circuit. That's probably what ruined the relay. What I would do is unplug the wiring harness from the blower fan and see if it stops blowing fuses. If it does, you likely need a blower fan. Mine's never given trouble but there are people here who can help you through that job. If it still blows fuses with the AC blower motor unplugged, I'll pull out the schematics and we can go from there. -- Click Here for CaddyInfo page on "How To" Read Your OBD Codes-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data -- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC Yes, I was Jims_97_ETC before I changed cars. Link to comment Share on other sites More sharing options...
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