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So I have multiple issues I’m trying to solve. The first issues I have is the check engine light is on and my scanner shows a P1175 code. Now, it also had a P0174 before I cleared the codes after cleaning the Mass Air Flow Sensor and checking for vacuum leaks, But the P0174 has not returned yet. The P1175 has returned and along with it the freeze frame data my scanner captures for fuel trims indicate a lean condition(plus 20something on LTFT). I did a smoke test and could not find any leaks thru the intake plenum and I cleaned the MAF sensor yesterday. I replaced both downstream O2 sensors, and replaced all plugs and wires about a month ago. I also had to drop the fuel tank and replace the fuel pump due to a leak last summer. The only other thing I can think of replacing is the 2 upstream O2senors, but I want to be confident that that will correct the problem. Now the second part of my problem is my scanner will not communicate with the ECM to read live data so I’m not sure of the particulars other than the freeze frame data it captures when the code was set. Any advice on both of these problems would be greatly appreciate. I’m really clueless as to where to start with scanner not communicating, but it’s capturing codes and freeze frame data. It also seems to connect and read all other modules. I did find a trouble code in the EBCM module (U0073) and cleared that. And finally, the scanner I have is an AUTEL MAXIdiag.
Is the PCM in fuel control? In other words, do the front O2s shift properly between 200 and 800mV with these huge fuel trim corrections? Adding extra fuel into the intake will make the O2 react accordingly?
Not sure about this scanner, does it only cover generic OBD2 or does it also comunicate with the OE protocol?
An expert is someone who knows each time more on each time less, until he finally knows absolutely everything about absolutely nothing.
As for covering Generic vs OE. I believe it covers OE. Could you eloborate on the OE Protocol?
If it has O.E. coverage it should also have the ability to connect as generic OBD. Since you mentioned an EBCM code you went in on the O.E. side if the tool has one. Or it might be one of those code readers with ABS and SRS coverage??
You'll have to read the user manual to find out what the tool can do. If it has both O.E. and generic OBD capability try the other one to see if you can get live data that way.
O2S1 2 is Bank 1 Sensor 2. You want O2S2 1 for the upstream Bank 2. And I think the shrt-ft 1-2 PID is your Bank 1 Downstream O2 trim. See if you can find a shrt-ft 2-1 PID. Guessing that'll be what the tool calls Bank 2 upstream short term trim. Also take a look at your long term trims and downstream O2 on Bank 2.
Obviously the condition is affecting both cylinder banks. How are the (total) fuel trims over a broader rpm range/higher loads? What is the load pid on the freeze frame.
If the MAF works correctly then engine is suffering a fuel delivery issue, if it worsens under load you may want to look into injectors and pump. If it it hasn't been done in a while an injector cleaning service might be very helpful.
Maf readings at idle should hover around 1 gr/sec for each liter of engine displacement and it should reach 40gr/sec at 5000 rpm WOT, again for each liter of displacement. Working with frequency you want to see at least 2400 hertz at idle and close to 8000 hertz at snap throttle ( the last may be dificult to achieve if the throttle body control takes over....)
Are you able to scope secondary ignition?
An expert is someone who knows each time more on each time less, until he finally knows absolutely everything about absolutely nothing.
Last edit: 2 years 10 months ago by juergen.scholl. Reason: specs
So I came out to start vehicle and gather more info and the Check engine light is out now.
Stats this morning:
MAF AT idle is .01 lb/s or 4.536g
MAF at 3000rpm .05 lb/s or 22.679
not sure what you’re talking about when referencing frequency? What parameter should I be looking under!
Don’t think the injectors ever been cleaned.
And I replaced the fuel pump assembly last summer after I found a cracked/leaking line on the top of the unit which is in the tank.
Freeze frame data below:
LTFT B1=18%
LTFT B2=19.5%
Absolute load value was 65.9%
Calculated load was 89.4%
What did the oxygen sensors say? All 4 of them. Was the front 2 pegged lean? Check for any tsb reprogrammings or anything? Check the exhaust for leaks around the oxygen sensors
From what I can tell the O2 sensors are ok…the up stream fluctuate between 8 & 2mv and the downstream hold steady around 6mv-7mv.
I did find a TSB on injector cleaning. However it appears the recommended tool cost $3200, and this amount would not be something I would entertain as a DIYer. It would be cheaper to replace all 8 injectors. Any suggestions how to clean the injectors on the cheap? I already ran 2 bottles of LUCAS thru the tank and that was approximately 2 months ago. Obviously that didn’t work.
