99 Tahoe fuel pump ?

99 Tahoe 4 dr. 4 wheel drive LT will not start Thinking fuel pump needs replaced it will not start, no humming coming from the pump when key is turned on was told that the relay controls the hum that the fuel pump makes but relay when key is turned to start will click 2 times Got it to start and drove to advanced auto the codes they got were CO281 -- CO225 and PO129 they cleared the codes don't know what the C codes are ? 5 miles from home truck just stopped called AAA now friend came by and a code PO122 comes up and check gauges still a no start I don't have all the fancy gauges to check things with only a multimeter any help Please - Thanks in Advanced

Assuming the 5.7 motor? Is your Tahoe a New Body Style or Old Body Style.

The C codes are anti-lock brake codes. C0225=LF wheel sensor open. C0281=Brake switch circuit

P0129 does not show in my '98 service manual, but google says it's related to the MAP sensor. P0122=TPS low voltage.

1st thing I would try is replace the fuel pump relay. Just because it clicks doesn't mean it's sending the power to the pump.

Old Body vs New Body is important for me to be able to help. My manual is for Old Body only.

Yes it's a 5.7

I don't know if it is new or old body style
enclosed a couple of pics, or how do I tell if it's old or new
I have asked and 1 said old 1 said new
I was thinking about the fuel pump relay as I thought was was to keep clicking

the fuel filter is new well I replaced it 5 months ago
would the map or TPS cause problems with fuel


Thanks for any help
Don't know if I'm up to dropping the fuel tank and really can't afford the 8 hundred they want and that's if I buy the fuel pump then no guarantees cause I bought the part and not hiring no shade tree mechanic been screwed by them enough

It's an OBS (looks like a '97). '98-'00 was a transition from OBS to NBS. My Sub was a '99 VIN'd OBS. A friend has a '99 VIN'd NBS Another has a '00 VIN'd OBS. Because of this it is important that whatever you buy or order you must include the VIN!! OBS vs NBS = Way different electronics and controls.

Lots of stuff (trouble shooting) to go thru before you replace the pump.

I would suggest a subscription to AllData so that you can follow the steps outlined instead of "throwing" parts at it. It will save you money in the long run.

Check it out. http://alldatadiy.com/

Whenever you are in No-start do either of these to prove FP failure.

!. Spray carb cleaner in air inlet at air cleaner- then try to start- if it runs for a few seconds and dies- then you have a fuel delivery issue.


2. As you crank the starter, have someone Whaaaaap the fuel tank with the palm of their hand (or use a rubber mallet) if truck starts and runs, you have just confirmed your fuel delivery issue is your dead No starting to run FP. I have driven several cars/trucks home after a good Whaaaap on the tank- because it jars the pump, and centers the armature in among the brushes and the pump runs- until the next 10 or so starts and it does it again....I've never seen the FP relay be the issue- always the FP in my 35 yrs of testing.

It is just like a blower motor that goes bad-- you have to kick it to start it sometimes.

Thank You for your help so far
I guess it would matter also that it is a police package
at least it did when I put new brakes on it
I will check out alldata tomorrow evening after work



figure will clean the map sensor
and figure out the TPS also

and stop at Discount auto after work tomorrow and get a new fuel pump relay
brake codes will have to wait
any other help you can throw my way is appreciated

I will also try the carb cleaner and hit the gas tank
can't hurt at this point don't think
guess your saying if it dies right away it's the fuel pump after I spray carb cleaner

I will also try the carb cleaner and hit the gas tank
can't hurt at this point don't think
guess your saying if it dies right away it's the fuel pump after I spray carb cleaner

do not use any carb cleaner . this will damage all the plastic/rubber parts..
use starter fluid spray to see if it will start.. then you know its a fuel problem.

only use MAF cleaner on the MAF .. if you use the wrong solvent it will kill it.
electronic components will get damaged using the wrong solvent.

can be a wiring problem check the fuel tank wiring and grounds around the fuel tank. can be the ignition switch .. need a volt meter to see if the fuel pump relay get volts to the contacts that supply power to the pump.

you can use a jumper fused wire to connect power to the fuel pump .. this will bypass the PCM and other electricals that control the pump.. use a 10 amp fuse on the jumper wire..

I had a erratic start issue with my 96 Impala .. it was the fuel pump relay ..

the other cause of the engine dying if not a fuel issue the ICM .. when the ICM gets hot it will not provide spark .. if its 20 yrs old replace it ..also check the IG coil for arcing ... small arcs will kill the ICM..

...I've never seen the FP relay be the issue- always the FP in my 35 yrs of testing.

You've been lucky. j cAT shows one example, I have two others with my OWN vehicles, not counting vehicles I service for others.

Here is the result of one - Having to install an auxiliary relay to handle the pump load due to the inability of the factory wiring to handle it reliably:

http://www.wwdsltd.com/files/262V6FPLoadRelay.jpg

never replaced a fuel pump on my vehicles .. well not the in tank fuel pump... but I did have to replace 2 fuel pumps mounted on the engine back in the carb days..

probably why I never had to replace in tank fuel pumps is ,, replace the fuel filter 20K miles and I keep the fuel level 1/3 to 7/8 ... never go below 1/4 ..

on the Impala that tank is not designed for in tank pumps so I keep it never below 1/2 .. also the fuel level sender is a problem .. it indicates more fuel in the tank than the dash gauge ...

that Impala relay is the same as the interior lamp/light control .. so I swapped the relay and never had any start issues... bought a new relay .. contacts on a DC motor controlled by relay will get pitted then the poor current flow..
the Impala fuse block is in a very hot area so the relays do have problems .. electric fan relays also fail due to the heat. GM TSB on this ..

Sorry I haven't updated any, not been on line

had to fly North as my Dad is not doing well
hoping to get back home within the next week or 2 not sure
I do appreciate the help and input
give me some thing to look at or for


I have been told by my Dad that Autozone has a loan a tool
and you can rent the fuel pump diagnosis kit for hundred bucks
and get it back when you return it Will check it out when I get home, nice to know


Any more input in the mean time is appreciated

Sorry I haven't updated any, not been on line

had to fly North as my Dad is not doing well
hoping to get back home within the next week or 2 not sure
I do appreciate the help and input
give me some thing to look at or for


I have been told by my Dad that Autozone has a loan a tool
and you can rent the fuel pump diagnosis kit for hundred bucks
and get it back when you return it Will check it out when I get home, nice to know
Any more input in the mean time is appreciated

use your Credit Card to get the fuel pressure gauge at AZ. they will not put a charge on it unless you do not return it.. gauge cost is $40 approx..
pressure should be 53-60 psi ..eng on .. key on eng off 60-65psi and should not drop more than 10 psi.. if the fuel pressure is good then an electrical problem .. or a PCM problem connector corrosion .. your area is a wet spot and many have had connector corrosion [green] on the pins.

Well just got back home going to autozone in the morning and test the Tahoe
see what is what, called and they have it reserved for me to pick up first thing
it seems to be loaned out alot, don't know if there is a way to test it in store to make sure it's not defective

Well it is the fuel pump, gotta get a 1/2 tank of gas out of there, I never go below a 1/4 of a tank and then double check to make sure it is the correct 1
99 old body style police package 4 wheel drive I have heard alot of people say rock auto is the place to order from, but really think I would like to do autozone or last choice advanced auto as they have went down in quality of the parts and service I think

Well it is the fuel pump, gotta get a 1/2 tank of gas out of there, I never go below a 1/4 of a tank and then double check to make sure it is the correct 1
99 old body style police package 4 wheel drive I have heard alot of people say rock auto is the place to order from, but really think I would like to do autozone or last choice advanced auto as they have went down in quality of the parts and service I think

advance auto is not good now .. one store in my area did have good service but the parts are not good and they will sell a part that was returned defective to you ..
last time last year I was buying an alternator .. alternator was defective so they were nice and gave me another .. on the counter I opened the box and the pulley was bent .. not good..

Advance will not sell parts that have been returned. My cousin is a manager at one and parts that are returned are either sent back to the manufacturer or they are defected out.

Also the parts Advance sells are no different than the ones sold by Auto Zone, O'Reilly's or even Rock Auto. With any electrical part it is always a crap shoot no matter where you buy it from.