Code 51, hypothetically assume all other systems (tps, etc.) are in good working order. Can NOT having the a/c compressor connected trip this code?

the t3d

the t3d

P B4 A
Sep 30, 2006
839
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Titusville, FL
My A/C compressor is no longer installed, so I am just trying to eliminate any oddball items I might be missing. But if this can trigger a code 51, how do you go about addressing that? Once this question is answered I can continue on with the root cause of this code, but for right now I would just like to focus on this particular interaction.

Just so it is stated, the TPS has been replaced. The TPS has been calibrated at least twice per the TSRM with no change. I've replaced the TPS connector and some fresh wire close to that connector. To finish ruling out the wiring to the TPS I'm going to create jumper wires straight to the ecu, and that will rule out the stock harness wiring be faulty.

The other situation that makes this a little more challenging is that is an auto to manual converted car, with an auto ecu. I'm thinking the ecu not receiving the "NSW" signal is also a possibility because of the manual conversion.

Lastly, I've swapped the ecu out and still had the same problem, so I can rule that out as well.

1677115444148.png

As I look at my snippet, it is telling me that if I can identify which of those three signals I am not getting at the ecu connectors that will direct me more to where I want to look, correct? If so, are those 5V signals I should be able to pick up on a DVOM?


Also, I am rocking the 7MGTE and my baby is a 1987 HT. I feel that needed to be mentioned.
 
F

figgie

Supramania Contributor
Mar 30, 2005
5,225
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Twin Cities, Minnesot-ah
the majority of time, Code 51 is due to an incorrectly calibrated TPS but looks like you have that covered.

The neutral start switch from the auto will more than likely be your culprit.

You will need to check and make sure you have continuity as followed (might require jumpers).

1677273217878.png
The AC signal comes from the climate control board and not the compressor etc.
 
the t3d

the t3d

P B4 A
Sep 30, 2006
839
1
18
Titusville, FL
figgie said:
the majority of time, Code 51 is due to an incorrectly calibrated TPS but looks like you have that covered.
Just because I'm crazy and it's been over a year, I am going to do the TPS jumper wires, as well as a re-calibration just to cross it off this new list.
Click to expand...

figgie said:
The neutral start switch from the auto will more than likely be your culprit.
When I first bought the car back in 2008 the owner said he bypassed the neutral start switch. I feel like this was probably the reason when I converted it to manual, pushing the clutch in to start was never needed, unless that is just a result of doing that swap regardless. And if someone WAS to bypass the neutral start switch, how would you do that? And if jumpered/bypassed, would it tell the computer the car is always in a Park/Neutral position? That's what it needs to see to NOT trigger the code 51, yes?
Click to expand...
I also found this in the TSRM...
1677349404975.png
figgie said:
You will need to check and make sure you have continuity as followed (might require jumpers).
Just bookmarked this in the TSRM.
Click to expand...

figgie said:
The AC signal comes from the climate control board and not the compressor etc.
Would pulling the A/C fuse and/or disconnecting the climate control head unit eliminate this variable?
Click to expand...

Also, I appreciate the help!
 
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