OBDII LT1 Tuning Issue - can anyone help?

**turbojimmy** · 12-02-2010, 06:37 AM

I realize this isn't an LS1 issue, but I'm getting nothing over at ls1lt1.com.

I have a 1996 Cadillac Fleetwood with an OBDII LT1. It was running crappy but I had to get it through state emissions inspection (read: I needed to make the Service Engine Soon light go out).

A GM TSB allows for the elimination of the Secondary AIR injection system. I had the dealer perform the work and flash the PCM. This cleared the Secondary AIR injection error code I was getting. *Everything functioned normally after the dealer reflashed the PCM* (this is important later on)

I still had an EVAP and misfire code that wouldn't go away. I knew I had a bad cylinder in the engine but didn't have time to repair it. It still ran halfway decent so I continued to drive the car. Desperate to get a good inspection sticker, I had a mail-order tune done on the stock PCM to eliminate the Secondary AIR injection, misfire reporting and EVAP functions.

While I was waiting for the mail-order tune to be shipped back to me, I installed a PCM out of a 1996 Chevy Caprice. The car functioned EXACTLY as it did with the stock Cadillac PCM and threw the same codes as before (AIR injection, EVAP and misfire).

When I got the "tuned", stock PCM back I popped it in along with a good-running LT1 engine out of a 1996 Caprice. In functioned exactly as it should: no codes despite the non-functioning EVAP and AIR systems. BUT, and here's where it gets interesting, my primary cooling fan came on at startup and the secondary cooling fan came on at 180 degrees. The tuner said they should come on at 198 and 205, respectively. Also, the Cadillac is smart enough to wait for the coolant to reach around 95 degrees before it turns on the heat. Not anymore - it's coming on early and blowing cold air. I figured the Engine Coolant Temp sensor was bad on the donor engine. I swapped it for the Caddy sensor. No dice. I then swapped it for a new GM sensor. No dice.

For grins and giggles, I removed the "tuned" PCM and replaced it with the Caprice PCM. Everything went back to normal.

Since the new engine was running really well, I figured I'd give the tuner guy another shot at fixing whatever was going on with the fans. Plus, I had misfire reporting disabled and I wanted it turned back on. The tuner guy was hoping that the disabling of the misfire reporting might be causing the odd fan behavior and that re-enabling it would fix it.

I got the second version of the "tuned" PCM back yesterday. I got a "power tune" with it, and have Secondary AIR and EVAP reporting disabled. The car runs AWESOME but....still strange fan behavior.

On the Caddy I can view the coolant temp as reported by the PCM through the HVAC controls. The first problem I see is that at low temps it's reading high. For example, this morning it was 28 degrees outside. After the car sat all night, the coolant temp showed 59 degrees at start up. When it warms up, though, the reported temperature is more believable. It tops out at 180-182 degrees, which is the thermostat temp. With both fans running at full speed, I can see why it would hover at 180 degrees. This still doesn't explain why the fans are coming on before the programmed thresholds are reached. The tuner is adamant about the 198 and 205 degree turn-on thresholds. But it's just not behaving that way.

Again, when I pop a stock, unmolested PCM in, it all works fine.

So....the question is: what could this tuner be doing that is causing the PCM to misinterpret the ECT data? He's at a loss and so am I. I need to have a PCM that has the EVAP and AIR disabled!!! Plus I like his "power" tune - the car runs noticeably stronger. It's a limo so it needs all the juice I can wring out of it.

TIA!!

Jim

**pajeff02** · 12-04-2010, 05:16 AM

The fan tables are pretty straightforward from what I recall and it is such a common mod to install a cooler thermostat that I assume your tuner is very familiar with them. However, I have no idea how things are done on an older platform though. Here's what my fan table looks like in HP Tuners:

**turbojimmy** · 12-04-2010, 05:41 AM

Originally Posted by pajeff02

The fan tables are pretty straightforward from what I recall and it is such a common mod to install a cooler thermostat that I assume your tuner is very familiar with them. However, I have no idea how things are done on an older platform though. Here's what my fan table looks like in HP Tuners:

Thanks for that. The tuner got in touch with the guy that wrote his software. Turns out there was some information that wasn't viewable in the software that could be Cadillac or D-body-specific. It has to do with the fans running in 'protect mode' when certain trouble codes are present.

I have secondary air injection and EVAP disabled, but I guess the PCM is still looking for them but the error codes are suppressed? I dunno. Somehow the dealer was able to delete the air injection without this issue. In any event, he thinks he has a fix. He's gonna send me his kit for me to flash it myself.

Jim

**turbojimmy** · 12-30-2010, 03:26 AM

Ok, here's what the problem was. Looking at the calibration file in JET DST (Tunercat), the fan settings appear as "Fan 1 On Threshold (Low MPH)", "Fan 1 On Threshold (High MPH)", "Fan 2 On Threshold (Low MPH)", "Fan 2 On Threshold (High MPH)". You populate the temperature in Celsius in each field.

This doesn't make sense to me. The way HPTuner has it makes more sense to me since there is a field for the turn on temp and turn off temp for each fan. I don't know what MPH has to do with it or where you would program the turn off temp using the JET DST. But I digress....

The original dealer calibration had the same values in both the "Low MPH" and "High MPH" fields for each fan. My "tune" did not. Setting the values the way the dealer (albeit lower so the fans come on sooner) caused the fans to behave properly.

The only other thing I did was disable traction control since my car doesn't have it. I don't think it has anything to do with anything, but I figured since it was an option I'd eliminate it. My Cadillac is a limo and therefore has the traction control and ABS deleted (my tuner had no way of knowing that).

**pajeff02** · 12-31-2010, 05:49 PM

Originally Posted by turbojimmy

I don't know what MPH has to do with it or where you would program the turn off temp using the JET DST. But I digress....

The MPH setting is important as it disables the fans at higher road speeds. There is sufficient airflow through the radiator once a predetermined speed is reached such that the fans become ineffective and do not add to the total airflow.

**turbojimmy** · 01-02-2011, 12:12 PM

Originally Posted by pajeff02

The MPH setting is important as it disables the fans at higher road speeds. There is sufficient airflow through the radiator once a predetermined speed is reached such that the fans become ineffective and do not add to the total airflow.

Well that I understand, but I don't understand the temperature-controlled turn on settings that have "High MPH" and "Low MPH" in their descriptions. Here is a list of all of the fan parameters from my stock (dealer installed) calibration file:

Fan 1 On Threshold (Low MPH) 107 Deg C
Fan 1 On Threshold (High MPH) 107 Deg C
Fan 2 On Threshold (Low MPH) 111 Deg C
Fan 2 On Threshold (High MPH) 111 Deg C
Fan Hysteresis Low Speed (MPH) 4 Deg C
Fan Hysteresis High Speed (MPH) 4 Deg C
Fan Threshold High Speed (MPH) 15 MPH
Fan 1 On, Oil Temp, (Low RPM) 164 Deg C
Fan 1 On, Oil Temp , (High RPM) 164 Deg C
Fan 2 On, Oil Temp, (Low RPM) 164 Deg C
Fan 2 On, Oil Temp, (High RPM) 164 Deg C
Fan Oil Temperature Hysteresis 0 Deg C
Fan Enable, (High RPM, High Oil Temp) 6375 RPM
Fan 1 On High A/C Pressure Threshold 225 psi
Fan 1 Off High A/C Pressure Threshold 180 psi
Fan 1 Disable MPH, High A/C Pressure 77 MPH
Fan 1 Enable MPH, High A/C Pressure 74 MPH
Fan 2 On High A/C Pressure Threshold 248 psi
Fan 2 Off High A/C Pressure Threshold 203 psi
Fan 2 Disable MPH, High A/C Pressure 75 MPH
Fan 2 Enable MPH, High A/C Pressure 72 MPH

The first 4 are what were causing the fans to run all the time (but not in this file - this one is okay). What is the "High MPH" and "Low MPH"??? It looks like the hysteresis dictate when the fans shut off (a 4-degree celsius window)?

EDIT: So it looks like the "High MPH" is 15. Below that, presumably is "Low MPH". I think I'm catching on....

**pajeff02** · 01-02-2011, 03:23 PM

After clicking on "System" and then selecting the "Fans" tab, look for the gray information box at the bottom. As you mouse over the different parameters it gives a brief description of their function.

**turbojimmy** · 01-03-2011, 12:11 PM

Originally Posted by pajeff02

After clicking on "System" and then selecting the "Fans" tab, look for the gray information box at the bottom. As you mouse over the different parameters it gives a brief description of their function.

I don't see anything like that in the software they sent me. Here's what I've got:

If I click on Constants, then System Parameters it will give me a list starting with the fan behavior. But, if I roll over any of it there's no info. Maybe they have a newer version I can upgrade to?

Thanks,
Jim

**pajeff02** · 01-03-2011, 12:18 PM

Totally different software. No idea on that one.

**turbojimmy** · 01-03-2011, 12:19 PM

Originally Posted by pajeff02

Totally different software. No idea on that one.

I'll goof around with it. Thanks anyway!

**turbojimmy** · 01-05-2011, 05:01 AM

Just for fun, I yanked the stock calibration from my '02 Trans Am. Got totally different fields. It's kind of neat. This layout makes much more sense to me. Fan on, fan off. Very simple. And nothing I had to go to dictionary.com to look up (hysteresis).

Fan 1 On Coolant Temp. 108 Deg. C
Fan 1 On Coolant Temp - A/C On 0 Deg. C
Fan 1 Off Coolant Temp. 104 Deg. C
Fan 1 Run-on Coolant Temp. 113 Deg. C
Fan 1 Keyoff On Time 150 sec.
Fan 1 On A/C Pressure 215 Psi
Fan 1 Off A/C Pressure 190 Psi
Fan 1 Off Vehicle Speed - A/C On 35 MPH
Fan 1 On Vehicle Speed - A/C On 30 MPH
Fan 1 On Minimum Engine Run Time 0 Sec.
Minimum Fan 1 On Time 50 Sec
Minimum Fan 1 Off Time 1 Sec
Fan 1 Turn On Delay Time 0.5 Sec
Fan 1 Turn Off Delay Time 0.2 Sec
Fan 1 Off Delay After Fan 2 Off 1 Sec
Fan 2 On Coolant Temp. 112 Deg. C
Fan 2 Off Coolant Temp. 108.5 Deg. C
Fan 2 On A/C Pressure 248 Psi
Fan 2 Off A/C Pressure 208 Psi
Minimum Fan 2 On Time 30 Sec
Fan 2 On Delay Time 1 Sec
Fan 2 Turn On Delay Time 0.4 Sec
Fan 2 Turn Off Delay Time 0.3 Sec
Fans Off Vehicle Speed - A/C On 65 MPH
Fan Type (0=2 Fans, 1=Aux Fan, 2= None) 0