96 – 07 GTP Model Differences

’97 vs. ’99 Grand Prix GTP Throttle Body.

1997 marked a new beginning for the Pontiac Grand Prix. This model year marked a complete chassis, body, and drive train redesign. They picked a winning combination and have been using this setup for the last 5 years. This article is about the changes that have taken place in the current body style.

1997

• Master cylinder/fluid reservoir setup is different than on newer years.
• Antenna on rear fender instead of in rear window on most 97s.
• Unique PCM for this year only, removable chip making case learn unnecessary.
• Large windshield washer fluid reservoir on top of battery.
• Alternator and mount is different than the newer years.
• Coolant temp display in the car starts at 100.
• * The 97s DO NOT have tire pressure sensors. The 97s have the Delco Delphi ABS system, which could not handle the GTP power for TCS. So TCS was disabled on the 97 GTP, but works on the GT and SE. The “Tire Pressure” light was part of the Delphi ABS system; it did not sense pressure but noticed differences in tire rotation speed. When the Delphi was replace with Bosch, TCS was enabled but the “tire pressure” light was lost.
• * Some of the 97s had a prop rod instead of struts to hold up the hood. Some had under hood lights, too. The under hood lights were phased out after the prop rod, so few have both struts and an under hood light.
• * Rear fender mast antennas were common for 97s because they ran out of rear window antennas at the factory. Those with mast antennas were credited $15 on the sticker.
  *Courtesy of Gene Orlanes
• Transmission input shaft is a little stronger from a better O-ring groove radius.
• Complex EVAP system that uses an extra part not found on newer GPs.
• M90 has an extra vacuum port.

1998

• Fixed the problem with the fuel level sending unit.
• Larger gas tank.
• New PCM used through current models with some minor changes each year.
• Coolant temp display in the car now starts at 160.
• New shrouding and mounts on the fans to make them more efficient.
• Moved the windshield washer reservoir into the passenger fender.
• * Side mirrors on the 98+ and some retrofitted 97s have a little lip underneath to reduce wind noise.
  * Courtesy of Gene Orlanes
• Performance shift indicator light added to gauge cluster.
• Last year of GTP being an option for a GT (makes a difference with insurance).
• * Daytona Package available (Blue Pace Car Daytona Edition with torque star rims).
  * Courtesy of Charles Beyer
• Went to Dual digital climate control.
  * Courtesy of Charles Beyer
• 98+ the gas cap is tethered to the fill tube.
  * Courtesy of Gene

1999

• Fixed the headlight condensation problem.
• Better air box (5hp), draws air from behind headlight and uses larger filter.
• Moved coolant tank reservoir to side of strut tower.
• Different Throttle body. Same electronics & mounting but the MAF sensor is setup differently.
• Torque star rims available that to date are the lightest offered on a GP.
• Fixed the problem with the fuel pump resistor.
• Fixed a problem with the wipers malfunctioning.
• The light color went from green to red in 1999 on the digital climate control.
  * Courtesy of Trend1
• Bose sound system was added in 1999 as an option for the first time.
  * Courtesy of Trend1
• From 99 on, the Trans shifter cable became shorter and routed differently than the previous years (behind air box rather than around it)  *Courtesy of Steve Widerski
• I thought I would add something to this subject. In 1999 the “Gold” package was introduced. The option code is Y11. It was available for only two years, 1999 and 2000, and only on the GTs and GTPs. It included gold striping, black and gold badging, black and gold wheel center caps, and gold wheels. In 1999 the wheels were painted and in 2000 they were anodized. As far as I know, this was a Canada option only. It is listed in the Canadian brochure, but not the American brochure. I own a 2000 GTP Coupe with this option. I have all the GM Canada documentation for my car. Only 25 were produced.

–   Roland Loewen, Canada

2000

• Added a small reservoir to the fuel line on top of the SC.
• More plastic shrouding in front of the radiator.
• * Added the child seat anchors on the package shelf.
  *Courtesy of Shawn Leichliter
• * Went from Passkey 2 to Passkey 3.
  *Courtesy of Richard Chu
• In 2000 the dual digital climate control’s previous “AC” button has been renamed “ECON” and the LED indicator works opposite, lighting up when the A/C is cancelled, rather than lighting up when it’s working, like in prior years.
  – Courtesy of Mike Watkins

2001

• The injectors and injector wire plugs were changed on the L36.
• * Different sun roof cover, that doesn’t split in the middle, making it look like two pieces. It instead, looks like one solid piece. There are vents in the cover near the handle. These vents are nice since you can crack open the sunroof just so it lifts up in the back, and keep the cover closed. This helps in the summer when you can keep the cover closed so the sun does not get in, but hot air can still rise up and out of the sunroof.
  * Courtesy of SnM
• On the 2001s, you have to disable each thing, by removing the connector to the diode in the dash for the DRLs, and you have to remove the light sensor in the middle of the dash for the auto headlights.
  * Courtesy of SnM
• On-Star cell phone antenna on rear window.
  * Courtesy of SnM
• Removed performance shift.
• Removed digital climate control.
• Replaced the lights in the doors with reflectors.
• On-Star now causing stereo installation problems.
• Went with a new steering wheel with a smaller center.
• * The 2001 cars have a deeper cup holder by an inch.
  * Courtesy of Kelly Lischka
• * Special Edition available.
  * Courtesy of Kelly Lischka
• New bracket on rear of coil pack mount.
• Switched to a plastic gas tank.
• The 1997 has 3 bolts that hold the hinge to the body of the car, whereas the 2001 only has 2. On the 1997 one of those bolt holes in the hinge itself are slotted, so to remove the hinge from the car you don’t have to fully remove that bolt, the other two you do. The 1997 hinge has rubber bumper stops in its down resting position and in its open raised position. On the 2001 model, it doesn’t have any rubber bumper stops whatsoever. It does have a bolt adjusting screw for the “down position” so the hinge doesn’t go too far down and do damage to the body of the car.
  – Courtesy of Jason Farnsworth

2002

• * 40th Anniversary Edition available.
  * Courtesy of Kelly Lischka

2003

• A pillar is changed so gauge pods will not fit.
• Transmission now has internal neutral safety switch.
• Outside temp sensor removed.

    Just did an analysis of the various PCM’s that the 3800SC engines used and came away with the following: My conclusion seems to agree with the information that you passed on.

The 4T65eHD’s up until 2002, all used transmission fluid pressure switches that were used to set the line pressure. In 2003 it appears that the transmission design was changed to incorporate a PC solenoid to accomplish this task.

A comparison of the PCM output diagram from 2003 to the 2004-2006 units  appear to show almost identical outputs to the tranny with a couple of exceptions.

The 2004-2006 PCMs  have a Remote Shift Selector signal that I believe is for the paddle shift option that the series III uses. The 2003 PCMs have a TCC Brake Switch Signal output which I don’t see on the 2004 – The 2003 PCM doesn’t output a Remote Shift Selector signal.  The 2004-2006 units do.

Therefore, a couple of assumptions can be made about using a 2003 PCM series II to manage the later 4T65e HD transmissions used on the series

III.

1. It appears that the change in controlling the transmission fluid pressure  was done in 2003 while the series II engine was still being used.

2. The 2003 PCM can probably shift this transmission provided that the PW modulation or control parameter  input to the PC solenoid valve HI/LO in/outs is the same as the 2004-2006 transmissions. We guess that it probably is unlikely that GM would make the change for one year only.

3. The Remote Shift Selector signal output is missing on the 2003 PCM (we assume paddle shift) so we will need to determine if the trans shifting defaults to automatic shifting without seeing it.

4. No surprise, but the pre 2003 PCMs WILL NOT SHIFT the late 4T65EHD’s  and it is very questionable even if internal mods can make the trans compatible with the earlier PCM.s

Ideally the next step would be to locate someone who has tried swapping the 3800SC series III /4T65eHD powertrain and running it with  the 2003 GTP PCM w cable style TB and sensors. If it can be done, this would get us away from trying to install with ETC (which is something that we want to avoid).  The swap would probably be successful using this powertrain with the 2003 PCM, Northstar TB, series II O2 sensors and the LS6 MAF, but a couple of questions remain before we attempt it. Seems like we may be the first folks to try it.

 If you have any more definitive information to share, please pass it along.

Regards, Dennis

3800SC series III /4T65eHD swap in progress