96-97 Fuel control

[RealMcCoy]

I feel a little dumb asking because I should probably remember this myself.... (we'll just blame old age...lol)

I was e-mailed a log from a 97 to help another member diagnose an issue, and the front fuel control has what looks like garbage data.

So the question is: Is the separated front/rear bank fuel control something that started with the 98-99? and there is only one bank of control on the 96-97?

[striker2]

all OBD2 vehicles should have separate fuel control as part of the emissions standards for OBD2, so anything from 96+. Easy way to confirm is to hook up a standard OBD2 scan tool that shows live data and look for B1 and B2 LTFT.

many manufacturers had split fuel control on their OBD1 computers if they had sequential port injection (instead of TBI). Im pretty sure Mitsu did on their US models (no reason to spend the money on the extra O2 sensor otherwise).

[RealMcCoy]

Not buying that... Almost all monitor the banks separately, but to see separate bank control and trims is pretty rare... Most cars that I see (even much newer than these cars) only have LTFT/STFT and BI/B2 trims are not supported.

I don't have a 96-97 here at the shop to check, so I can't verify it one way or the other.

[striker2]

The only OBD2 vehicles that might not have separate bank control (aside from the obvious I4 engines) are those that only have a single cat after the exhaust merges. many vehicles (including the 3S) have pre-cats, one per bank, plus the main cat and the PCM has to be able to adjust the banks individually to keep the pre-cats functioning properly (and from burning them up).

[RealMcCoy]

The only OBD2 vehicles that might not have separate bank control (aside from the obvious I4 engines) are those that only have a single cat after the exhaust merges. many vehicles (including the 3S) have pre-cats, one per bank, plus the main cat and the PCM has to be able to adjust the banks individually to keep the pre-cats functioning properly (and from burning them up).

I agree that would be the ideal method, but in reality it's seldom the case... While a large portion of the cars out there fall into the category you mentioned as merging into one monitored cat, there are many out there that have separate monitored cats, but don't support separate fuel trim data.

I don't believe OBDII mandates HOW the manufacturers control the fuel and cat efficiency, just that they do it, and set codes for failure... It's up the the manufacturer to meet the emissions standards of the model year being produced in any way they can.

OBDII was also quite slowly phased in and modified in the early years... It's pretty common to see very different standards for a 96 car than a 98...

But none of this theory positively answers my question... I have a log with both displayed, but complete garbage on the front bank, and relatively normal readings on the rear. I'm theorizing that it's just garbage on an unused PID, but it would be very nice to confirm it for sure one way or another..

[vr4tune]

I have a 97 and yes it has separate fuel controls as well as stft and ltft for both banks. I had a cracked front manifold and only my front bank went rich. It may be the scan tool.

[RealMcCoy]

I have a 97 and yes it has separate fuel controls as well as stft and ltft for both banks. I had a cracked front manifold and only my front bank went rich. It may be the scan tool.

Awesome, thank you... I agree now that I have that info. He's using evoscan 2.9. I told him it was broken, and to download an earlier version, I don't think he believes me yet...

[Greg E]

91 to 99 Turbo cars have separate bank fuel trim control. Hence there being 2 o2 sensors.

Later NA cars switched to dual bank control too.

[RealMcCoy]

91 to 99 Turbo cars have separate bank fuel trim control. Hence there being 2 o2 sensors.

Later NA cars switched to dual bank control too.

Few know the code like you do, so I won't argue... But I will submit that "contol" does not equate to available scan data... There is no separate right and left trims output in scan data for a first gen...

[Greg E]

Few know the code like you do, so I won't argue... But I will submit that "contol" does not equate to available scan data... There is no separate right and left trims output in scan data for a first gen...

It's because Jeff was the first person to discover it. Somehow this detail eluded all the software designers all these years. I think I'm the first person to trace the entire MUT table after Jeff got me started.