jmetz63 Posted October 26, 2009 Report Share Posted October 26, 2009 I am looking for a some help figuring out a friends STS issues. He has a 1993 STS with the 4.9 Northstar and it has some bad idle and drivability issues. I pulled the computer codes and found a multitude of them. code 15- coolant temp low or short code 16- battery voltage to high or low code 18-executive loop overrun code 19- fuel pump signal high or shorted code 60- cruise engaged with car not in drive code 88-torque convertor clutch (TCC) not disengaging(repeats twice) code 117- QDSM #3 output open or shorted While watching the datastream while car was running I noticed MAF readings slightly high 7.5 gps and that vehicle speed read 126 mph at idle in park. Was told ECU was swapped to try and correct issues but had no effect on way it ran or codes they got. Did notice that while removing spark plug wires one by one that removing #6 wire made no difference in the idle. Next step I figured on doing wa a compression test and replacing #6 coilpack, wire, ignition module and plug since I have the spares. Any ideas or suggestions would be greatly appreciated. jmetz63 Link to comment Share on other sites More sharing options...
BodybyFisher Posted October 26, 2009 Report Share Posted October 26, 2009 WIth the battery voltage code, have you had the battery load tested? Pre-1995 - DTC codes OBD1 >> 1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/ Cadillac History & Specifications Year by Year http://www.motorera.com/cadillac/index.htm Link to comment Share on other sites More sharing options...
Logan Posted October 26, 2009 Report Share Posted October 26, 2009 Cadillacs are very sensitive to proper voltage. Be sure the battery and cables are good. Next, I would try tap testing the PCM. While the car is running, tap on the PCM in different spots. Any stalls or 'burps' indicate a bad PCM. May also need a new PROM. The 125 mph in park is a clue to a bad PCM. Logan Diagnostic LLC www.airbagcrash.com www.logandieselusa.com www.ledfix.com www.ledfix.com/yukontaillightrepair.html www.ledfix.com/ledreplacements.html www.ledfix.com/j42385toolrental.html Link to comment Share on other sites More sharing options...
jmetz63 Posted October 26, 2009 Author Report Share Posted October 26, 2009 Going to replace battery on Thursday, load tested bad. Also will do tap test and let you know what happens. Was my first guess that I was dealing with a bad PCM. Thanks for responding so quickly. Link to comment Share on other sites More sharing options...
jmetz63 Posted November 17, 2009 Author Report Share Posted November 17, 2009 well, replaced battery, CPU, temp sensor, coil pack, wires and plugs. Thankfully we had all spares saved from another 4.6. Also found some vacumm elbows that had cracked and replaced them. Car is running much and codes have dropped to 4 now. code 15- coolant temp low or short code 16- battery voltage to high or low code 19- fuel pump signal high or shorted code 88-torque convertor clutch (TCC) not disengaging(but still repeats twice) Car runs good with a slight miss still. Did pull wires one at a time (again) and found little change when 6 was pulled. swapped wires, plugs with 4 and got no change. 6 still misfired. changing coil pack didnt help. Was also looking for some advise about unplugging the TCC. Read where it wont affect drivability except for a slight loss of mileage and final overdrive. Where is this magic plug located and any info on changing/unplugging would be appreciated Link to comment Share on other sites More sharing options...
adallak Posted November 17, 2009 Report Share Posted November 17, 2009 Check all the grounds you can find. The saddest thing in life is wasted talent Link to comment Share on other sites More sharing options...
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