CLASS RACER FORUM - View Single Post - LT-1 issue

John Nechiporchik · 04-14-2015, 11:45 AM

Following up on Alan's advise to track down the voltage loss at the TPS, I contacted a guy that Accel advised as a service rep for their product. I spoke to him several time last year when I was experiencing a no start condition and he was helpful
As I explained my low voltage to the TPS, he suggested unplugging the MAP sensor (which was getting a 5v input) and then checking the TPS input. Well, with both connectors disconnected (TPS and MAP), both input voltages from the ECM read 4.97 volts. When I installed the MAP sensor connector, the voltage to the TPS dropped back to 4.24V.
I checked the ECM ground which is directly to the battery and the ground from the rear of the cyl. head and all were clean and tight.
Would a defective MAP sensor cause excessive current draw and subsequently weaken the TPS input?? Not certain how that stuff works. The accel guy indicated the two circuits , although different pins in the ECM connector, have the same voltage reference source.
He indicated a ground problem or possibly a bad MAP sensor.

All input/experience appreciated.

John

04-14-2015, 11:45 AM	#32
John Nechiporchik Member Join Date: Mar 2007 Location: Grosse Ile Mi. Posts: 316 Likes: 84 Liked 13 Times in 7 Posts	Re: LT-1 issue Following up on Alan's advise to track down the voltage loss at the TPS, I contacted a guy that Accel advised as a service rep for their product. I spoke to him several time last year when I was experiencing a no start condition and he was helpful As I explained my low voltage to the TPS, he suggested unplugging the MAP sensor (which was getting a 5v input) and then checking the TPS input. Well, with both connectors disconnected (TPS and MAP), both input voltages from the ECM read 4.97 volts. When I installed the MAP sensor connector, the voltage to the TPS dropped back to 4.24V. I checked the ECM ground which is directly to the battery and the ground from the rear of the cyl. head and all were clean and tight. Would a defective MAP sensor cause excessive current draw and subsequently weaken the TPS input?? Not certain how that stuff works. The accel guy indicated the two circuits , although different pins in the ECM connector, have the same voltage reference source. He indicated a ground problem or possibly a bad MAP sensor. All input/experience appreciated. John