First Post! unfortunately its about a problem :/

'96 Discovery w/ 168k Miles.. Starting losing acceleration at random throttle positions, I'd let off the gas and it would fall flat to idle or stall on occasion and come right back to do it again a few moments later. I could also floor it and generally power through it but constantly drive around under acceleration.

Truck threw 3 TPS codes, p0122, p0121 and i believe p0122 again. I replaced the TPS and visually inspected the harness, cleared codes. Did not solve the issue.

I rewired the TPS directly to the ECU for the voltage input from the ECU to the TPS and the signal wire back to the ECU leaving the RB (Ground) wire alone as it acts as the ground for multiple components and I assumed I would have a lot of other faults if it where that cable.. Same problems.. throwing the P0122 Low Voltage code still.

Tapped the RB Ground at the ECU and wired the TPS directly to it to bypass any faulty ground points hopefully.. same issue..

At this point I'm going to replace the Mass Airflow sensor as I have a spare and try again.. after that I'm pretty stumped, I've been reading a lot about it obviously and see there are some ECM's that are causing a TPS issue? My other thought was something mechanical in the throttle body but it seems too definitive of a failure (ie: no gas, gas)

Hoping someone on here has some type of idea of where I should go with it next.. Thanks ahead of time.

 

Do you have ael? Big square charcoal canister?

 

Nope, removed and electronically eliminated.

 

Since you had ael , tps is electricly hooked to a sensor on the fuel sender on gas tank, it goes bad causing your issue

Go to back, pull carpet m access panel, unplug , it is shorting TPS voltage, even though I see you screwed with the wiring to ecu probly still the problem, simple unplug the plug with the little vent hose

You may wish to restore the harness to its original state, no way you needed to mess with all that wireing, there's usually only a handful of issues on d1 don't think any require rewiring to ecm

 

Thanks a bunch for the insight Tom.. My tach was skipping around before I rewired the Red and Yellow green directly from the TPS to the ECU.. that fixed the visual tach jumpiness but not the actual issue of course.. I see in the RAVE the Red wire goes all the way back in the truck to show a 'Not Used'. I've completely bypassed that entire cable, is that the one that's known to go bad? The only original wire i have is the ground back to the ECU and I've cut it at the TPS and tapped it at the ECU but I imagine something could still be screwing up the ground maybe?

 

You have to look at the euro rave, the nas does not show that being used that's how I found it
That wire runs to a pressure sensor on the fuel sender, I would unplug it anyway see if it helps
Screwy tach is usually alternator issues and grounds

 

So.. to continue the saga, I found a guy with a proper reader and he determined the TPS at full throttle is only reading 40% and advised me to pull the ECU to see if its full of water as that was his only guess on why it wouldn't be reading properly after new wiring.

Sure enough.. its fairly corroded inside on the bottom corner, before I just put a megasquirt in this thing I'd like to attempt to retrace the bad connection that is visible to see how it does. But I can't for the life of me find any type of schematics or determine if this trace is a possible grounding spot too. Any Ideas or does anyone have a photo of a non corroded one?

 

Schematics of the GEMS ECM are proprietary and would not be freely available to the world even after this many years. Why not just fleabay or pick-n-pull another ECM before you squirt it cuz squirting it would take another year to figure out the parameters to get you out of single digit mpg........ A pro squirt box is $1500 by the way, kinda prohibitive unless your going to slam it for autocross.......

 

alright well.. i ran a jumper cable in the ECU to patch that trace that is missing.. cleaned up a lot of the corrosion etc.. didn't fix my current issue of a hunting idle.. but the tach reads pretty good and consistent? So probably fixed one of multiple issues.. I can no longer get my actron to pull codes so I probably screwed something up pretty good though. Going to try and get a better code reader to rule that out.

I've been reading about the immobilizer unit having control of the fuel pump along with it being a problem area and can cause a vehicle to cut out while moving as they get wet often?

I'm about ready to buy a spare ECU as well just to be safe.. just curious if I need to worry about this immobilizer syncing to the ECU or if its a hit or miss thing..

Any additional insight would be appreciated, This forum seems to be the most detailed with extensive knowledge in the user base.. which is why i'm here

 

Your truck would have had pre-AEL, the round coffee can and not the large square charcoal can the mid 97 thru 99 1/2's had. Just a clarification to others and what not...... There isn't a pressure sensor on our fuel pumps (or fuel tanks) tied to the TPS. Not a player.