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Every time I start my 1999 6 speed, it throws 3 codes:
P1120
P1220
P1516
I use my scan tool to clear the codes every time and the car drives perfectly fine.
However, if I turn off the car and turn it back on, the codes come right back along with reduced engine power.
This started after I installed a BBK throttle body. I reinstalled the original throttle body and the problem is still there. Then I reinstalled the BBK throttle body a second time making sure that all the screws were tight and the gasket was fine, and all the connections for the sensors were fine.
I used my scan tool to check the two throttle position sensors and they are both showing voltage within range and increase and decrease appropriately.
Here's what I know so far:
the two throttle position sensors are good, the fuse 17 is good, and the car runs perfectly fine if I clear the codes, until I turn it off and on again. I already performed the relearn procedure and I drove the car for a long time yet the codes still come right back on every time I turn on the car.
I don't know much about the TAC module. Is that a likely culprit for this issue?
The issue may be in the connector since you put the old TB on and you are seeing these DTC's...you using a Tech 2 or a scan tool that can graph the TPS 1 and 2 voltages??...I'd graph the sensor voltages and while you are wiggling the connector see if TPS 1 or 2 drop out or "glitch"...scan tool isn't as fast as a scope (scope takes a few million voltage samples per second) but you may see something...I did a quick "TPS Sweep" a while back on YouTube...this is what you should be seeing...you may want to see if these signal voltages are making their way back to the TAC module.
Okay I will check the graphs with my scan tool. For now, I removed the TAC module to check for any water contamination and it is completely dry. I will put it back in and then check the graphs.
And a good idea to check those 2 voltages at the TAC module…do you know which pins ??…you can back probe those 2 signal wires with your DVOM.
could you elaborate on that? Do I use a voltmeter to check the TAC module pins for voltage? If so, do you know which pins and what voltmeter setting to use? Or did you mean that I should use a scan tool to check the TAC after putting it back together
First I would check the 2 signal voltages at the TPS sensor with a DVOM...how did you know what the correct voltages are ??...the voltages should be these per the FSM and this is with the throttle plate manually closed and opened
These are what I saw KOEO and just pressing the accelerator down to WOT...I'd compare the reading at the sensor vs. the scan tool...see if you see the same voltages at the TAC module with your DVOM...pins 1 and 11 on the C2 connector. TPS1- IDLE TPS1- WOT TPS2- TPS2- IDLE TPS2-WOT
I recorded the data streams for both sensors while slow pressing and releasing the gas pedal with ignition on and engine off. When I completely let go of the gas pedal, sensor 1 is at 1.294v and sensor 2 is at 3.725v consistently.
when I floor the gas pedal, sensor 1 is at 4.157v and sensor 2 is at 0.843v consistently
It looks like our TPS1 voltages are a little off but like I said the numbers in the FSM are physically pushing the throttle plate opened and closed...have you see if you have any deposits on the TB bore ??...you can manually open the plate and use some TB cleaner (I.ve always used Brake Kleen) and see if the numbers changed...did you try wiggling the connector while looking at the scan tool ??
