Trailered GT to TN for car show and to visit family and friends in Ohio. Trailer sat in TN for 2 weeks before Pigeon Forge TN car show while I was in OH. First drive to breakfast at Pigeon Forge, I noticed boost gauge wasn't working and attributed it to a weak battery from sitting for 2 weeks. After the hour cruise on the curvy roads of TN to breakfast and after completing breakfast, started car for return trip and the gauge was working again. Drove car every day for the next 2 days without any problems. After another hour cruise to breakfast on the 3rd day and about 5 minutes after leaving the restaurant, the GT went into Limp Mode. Would not accelerate over 45 mph. Didn't matter what gear or RPM, it would accelerate strongly up to 45 and then start missing. No codes and no dash lights. Researched Forum with key word "Limp Mode" and couldn't find anything, so went to my Service Manual on CD and still couldn't find anything on Limp Mode. Thought to myself, battery is original Dec 2005 build (9 years old) combined with boost gauge symptom, so I must need a new battery. Tested battery and it was measured at 200 cranking amps and should be around 600+ amps.
Now the real challenge started with finding a replacement battery. Local area batteries had posts on top close to the edge of the battery which would not work because the posts would ground out on the metal panel under the radiator. The original Optima posts are about an inch away from the edge of the battery so they had adequate clearance from this metal panel. My research concluded that our original Optima batteries were built in Aurora CO, but the company was sold and moved to Mexico. Since the move, the Optima batteries have been very problematic according to my research, so I opted out of the Optimas. Finally found a battery with reverse polarity posts from the original (i.e. positive on left side of battery instead of right side). So I turned the new battery around in its mount to account for cable lengths and to get away from the metal panel. Now the 2 posts are facing the driver instead of facing the radiator. Used a Deca AGM 9A35/85, worked great. However, thought I'd be smart and hook up a battery to the OBD port to retain the car's computer memory when I changed the car battery. When I took the GT for a test drive, it was still in Limp Mode (45 mph max). Now what? Gave up trying to figure it out myself. Shadowman to the rescue!!! He said disconnect the battery again and wait 15 minutes, then reconnect battery to clear the fault codes even though no fault codes were shown on a $3500 scanner. Problem solved, no longer in Limp Mode. Shadowman is the man!!!!
Now the real challenge started with finding a replacement battery. Local area batteries had posts on top close to the edge of the battery which would not work because the posts would ground out on the metal panel under the radiator. The original Optima posts are about an inch away from the edge of the battery so they had adequate clearance from this metal panel. My research concluded that our original Optima batteries were built in Aurora CO, but the company was sold and moved to Mexico. Since the move, the Optima batteries have been very problematic according to my research, so I opted out of the Optimas. Finally found a battery with reverse polarity posts from the original (i.e. positive on left side of battery instead of right side). So I turned the new battery around in its mount to account for cable lengths and to get away from the metal panel. Now the 2 posts are facing the driver instead of facing the radiator. Used a Deca AGM 9A35/85, worked great. However, thought I'd be smart and hook up a battery to the OBD port to retain the car's computer memory when I changed the car battery. When I took the GT for a test drive, it was still in Limp Mode (45 mph max). Now what? Gave up trying to figure it out myself. Shadowman to the rescue!!! He said disconnect the battery again and wait 15 minutes, then reconnect battery to clear the fault codes even though no fault codes were shown on a $3500 scanner. Problem solved, no longer in Limp Mode. Shadowman is the man!!!!
Attachments
Last edited: