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Got a 99 chevy silverado 4.8 are lean bank 1 and 2 put fuel pressure guage on and reading 20 ilbs pressure jumps to 41 ilbs . then drops back to 20 ilbs could it be the fuel pump?

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My info says fuel pressure 55--62 psi. Yes, probably the fuel pump. Usually low pressure is a problem on the supply side. You can be thorough, check proper voltage and ground at fuel pump connector. Check inline fuel filter. I've checked inline fuel filters before where the fluid that ran out looked like dirty water. Don't take connections loose from inline fuel filter unless your sure, no pressure on the system.
You could block the return line, where applicable, momentarily, to see if pressure will go high. If not, it should be the pump.

Posted on Dec 15, 2016

Testimonial: "i appreciate your info,so just be sure i will probably change the filter and the fuel pump thank you"

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Replaced o2 sensor bank 1 sensor 1, now reading "Circuit Low Voltage Bank 1 Sensor 1" and P0154 on Bank 2 Sensor 1. Live readouts on both show avg of .48V. What is wrong?

Lets examine your readings first.
Code 154 means the sensor is not switching from lean to rich enough in 60 seconds. And there is no such thing as average voltage.
The O2 sensors generate their own voltage by measuring oxygen in the exhaust. They also have heaters that get power from a relay.
But a problem with the heaters should be a different code.
When the engine is running, the computer varies "on" time for the injectors based on engine temp, throttle position, and unburned fuel in the exhaust. So when the O2 sensors send voltage higher than .5 to the computer, the computer calls that RICH and shortens on time for the injectors. Then when the O2 sensor drops voltage down below .5 it reads LEAN, and the computer lengthens on time for the injectors.
This back and forth switching should happen several times each minute. Like the tick tock of a clock.
If the sensor(s) are slow to switch, or they stay on lean or rich for more than 30 seconds, you get the code 154. Each sensor has a different code for the same issue.
It could be a sensor problem, or a fuel problem, or something else.
Too lean can be low fuel pressure, too rich can be not enough air flow coming into the intake.

Apr 19, 2016 | 2000 Chevrolet Silverado 1500

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Codes 171 174 for 2005 suzuki verona l6 2.5 litre engine

ever give it a tune up this in the last 9 years.????
ah the 2.5, i have one too, the 2.5. and know it well.
i have the real FSM on this engine.
p0171 and p0174 (the zero counts) 02 reads lean, and LTFT slams to rail errors.

The FSM is clear, both banks are lean. BOTH is a key fact.
lean has many reasons, a mech , never just guesses why, there are 10 causes. or more.
what I do is get the engine fully hot.
Using any real scan tool (yes, you need a scan tool to fix all modern cars):
1: is the ECT showing over 180f +coolant temp? sure.
2: is the engine holding Closed loop at idle? no, fix that first.
3: i see LTFT , is trying to correct gloss lean. (bingo)
LTFT = long term fuel trim,
4: EGR cleaned, Does it leak.?
5: is the MAF dirty, the MAF sensor can go weak dirty and can cause low fueling , in FACT the MAF is the top fuel rate, device on this engine. 02 sensors are fine trim.
6: intake air leaks. any leaks cause lean.
7: low fuel pressure. for any reasons.

you posted only 2 codes.
and no driving symptoms, so ....????
loss of power WOT? wide open throttle?

the MAF is here.

page 34 , see it in the TB?
suzuki dont sell it,
take it off, and gently from 12inches away (never dead close at straw tip)
spray CRC maf cleaner on it , let it sit 1min, repeat and put it back.
i thne look for intake air leaks. under the TB side.
TB to the intake, and the whole behind TB side.
ok no leaks there.
i then check fuel pressure with a REAL guage.

that is just a start. we can take this to any conclusion
based on all tests. so far. then more tests. if need be.
this is called DIAGNOSIS.

Sep 20, 2014 | 2005 Suzuki Verona EX

1 Answer

99 s10 check engine light is on had it check out and codes came back p0171 and p0174 how can i find this leak

Lean bank-1 and bank-2, most likely a restricted fuel filter or low pump pressure.

Feb 23, 2014 | 1999 Chevrolet S-10 Pickup

1 Answer

2004 chevy silverado 5.3L V8 runs rough and stalls

Well, code 336 is for a problem with the crank sensor, and code 171 is for fuel system too lean bank one which is the side with cylinder one. Since you have checked fuel pressure and I will assume fuel volume is good, the crank sensor or circuit could be at fault.

Jul 09, 2013 | Cars & Trucks

2 Answers

1999 Chevy silverado 5.3 engine setting codes p171 p174 already replaced mas air flow and checked for leaks

oxygen sensor failure
P0171 System too Lean (Bank 1) - Read Our Article On Oxygen Sensor Codes For Help With This Generic Check Engine Light Code
P0174 System too Lean (Bank 2) - Read Our Article On Oxygen Sensor Codes For Help With This Generic Check Engine Light Code
hope this is a bit of a push in the right direction ...

Feb 02, 2010 | 1999 Chevrolet Silverado 1500

2 Answers

I have a 1997 chevy silverado putting out a code of p0174 what does this mean?

Basically this means that an oxygen sensor in bank 2 detected a lean condition (too much oxygen in the exhaust). On V6/V8/V10 engines, Bank 2 is generally the side of the engine that doesn't have cylinder #1.

A code P0174 may mean that one or more of the following has happened:

•The MAF (Mass Air Flow) Sensor is dirty or faulty. Note: The use of "oiled" air filters can cause the MAF to become dirty if the filter is over-oiled. There is also an issue with some vehicles where the MAF sensors leak the silicone potting material used to protect the circuitry.
•There could be a vacuum leak downstream of the MAF sensor.

Possible solutions include:

•In the vast majority of cases, simply cleaning the MAF sensor does the trick. Consult your service manual for its location if you need help. I find it's best to take it off and spray it with electronics cleaner or brake cleaner. Make sure you are careful not to damage the MAF sensor, and make sure it's dry before reinstalling
•Inspect all vacuum and PCV hoses, replace if necessary
•Check for a dirty fuel filter and proper fuel pressure

Jan 10, 2010 | 1999 Chevrolet Silverado 1500

1 Answer

I cant find out what is causing these lean codes on bank 1 &2.

vacuum leek,bad computer or you have a linkage out of adjustment on the throttle body

Feb 23, 2009 | 2001 Chevrolet Silverado 1500

2 Answers

Starts but well not stay running

did you check fuel pump relay?

Dec 19, 2008 | 1999 Chevrolet Blazer

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