I am a die hard chevy fan and I have just recently bought a 96 blazer with high mileage for 800 bucks. The previous owner said that the fuel pump was recently replaced and the fuel level gauge was actually stuck on half full. The other day when I was driving the vehicle I heard a loud clicking noise comming from the fuel pump relay under the dash, it was only clicking during acceleration and the engine was also surging/bucking during acceleration. During operation this does not happen when I was at a steady speed only during acceleration the engine would start "bucking" and the relay would start clicking like a machine gun, I also noticed that the fuel gauge went from stuck on half to stuck on past full. After driving the vehicle back home i attempted to park it and it idles up even with my foot off the accelerator, and now it will only start up with the relay clicking the whole time, idle up and down, then it will stall out. I replaced the relay and checked for any loose connections and I am still having the same problem. Right before this started to happen I also ran over a small curb but it didn't do any physical damage to the truck besides the fact that it stalled out and tranny fluid started leaking out by the tranny dip stick, not sure where though and if it is related to this problem because the relay didn't start acting up until after I parked the truck and started looking for this "leak" I had in. The engine compartment. I hope this doesn't sound too confusing but I tried to explain it as thouroughly as possble. I am young and I need this truck for school and work and I also have some automotive education. Any help would be greatly appreciated.


Also, these codes popped up after I checked the computer with a scanner for the first time..

po138 - bank 1 sensor 2
po144 - bank 1 sensor 3
po151 - bank 2 sensor 1
po174 - system 2 lean bank 2
po330 - miss fire/random mult
p1153 - manufact. control fuel & air metering
p1406 - manufact. control auxilary emission controls
p1870 - manufact. control trans.
po174 - system 2 lean bank 2

 

*cracks knuckes*

Your 02 sensors are bad. Replace them. While you are under there, clean / replace the wireing. They may be bad also. P0138/144/151 done.

I know the P0174 code personally...It means that you either have a vacuum leak (which would explain the high idle situation), and/or your MAF sensor is dirty, and is causing the wierd idle because it cannot monitor the airflow into your engine. Clean the MAF as a precaution...you should keep it clean anyways! Dirty MAF's kill your gas mileage!!!

P1153 is the dirty MAF...CLEAN IT! A trick for that is to take a gallon ziploc baggy, place your MAF sensor unit in it, and then fill the bag 3/4 of the way with denatured alcohol. Let it set for 30-60 minutes, shake it well, while holding on to the sensor, alowing the alcohol to move and swish around. Take it out, and GENTLY clean with a q-tip, or a tiny paint brush. Gentle is the word...very brittle platnum wires, very expensive part! Put on a towel, and air dry. Done!!!

Those above could cause the P0300. Actually, the P0300 code is still a mystery. It could mean that you need a tune up, or could be somthing as simple as a clogged fuel injector? I will let you do the searching on this website for that issue later Believe me, nobody has an answer. Everybody's P0300 is a different issue, but the same code!

P1406 is your EGR valve...cheap replacement ($50), or you can clean it. This could also cause a rough / high idle.

P1870 - Tranny...make sure it has fluid in it. It most likely needs to be replaced. Transmission fluid shouldn't just pop back at you from the dipstick. Check your levels first, before freaking out! Maybe the guy before you put too much in there, as a precaution, or something.

 

When retrieving DTC's you must start with the first one, diagnose and repair the problem, clear all codes and perform a drive cycle: http://www.obdii.com/drivecycle.html to confirm the repair. If any DTC's are set after the drive cycle, go through the process until no DTC's are set.

The first DTC retrieved can cause subsequent DTC's to appear, that's why they are diagnosed and repaired in order.

You might want to look into the clicking relay and screwy fuel gage before you go after any of the DTC's. A poor ground or poor connection could easily set numerous DTC's.

 

Thanks for helping me figure out exactly what those codes meant, I have a code reader but I just dont really understand the codes. As far as all the repair procedures go, thanks for the instructions, they seem pretty easy to understand, however, I can afford to replace all the O2 sensors, they arent cheap! As far as the transmission goes, I am not exactly sure where it was leaking from or even if it was from the dipstick. All I know is that tranny fluid was leaking out from somewhere near the dipstick, because the fluid was leaking onto the exhaust manifold and burning. There is a hose that was tied down to the dipstik tube, any one know what that would be? Also, is there a tranny cooler on this vehicle or any hoses that could be lekaing? The leak problem had been going on for a while now but it was intermittent and seemed to happen on isolated instances. As far as the Fluid goes, it was low so I added some more, and i guess the tranny was recently replaced by the owner before me.
Back to my biggest issue with the fuel pump relay, I dont think the issues with the codes are causing this issue because all the codes were present before this has happened. I did alot of research about this relay and found that it really should only be energized when the truck is first starting up. I think what is happening is that is continously trying to energize and make the motor on the pump run when it should be cause its ran off vacuum. From my research I have concluded that it may be the OIL PRESSURE SWITCH/SENDING UNIT, I feel that it may be this because I know that it is hard wired right into the relay and I also noticed the opil pressure go awfully high. As far as the fuel gauge goes, it was busted before I was having this issue but I also had just filled my gas tank up past full for the first time right before this issue started, so I dont know if it is related. I am going to try to change the switch this weekend, does anyone have any input on how the oil pressure switch would work. Alsom when I started the truck up the other day when it had been sititng cold for a while, it started up and idled fine and the rtelay didnt start acting up for a few mins, rather than in 10 secs. like it was before. Any help would be appreciated, thanks!

 

You are listing symptoms similar to what i experienced. Fuel gauge at 3 o'clock position, High surging idle, 3000rpm or so, loss of power intermittedly while driving. Multiple DTC...Low TPS input, Map input low ect. All these sensors use a 5 vdc refence from the ECM.. If any sensors short to ground it kills this reference voltage. FYI - The fuel level buffer also uses this 5 vdc reference. When i found the shorted sensor and replaced it, all my symptoms went away. Total cost??? $43 for the one failed sensor. I wouldnt start throwing parts at this thing yet until you do alittle research. Just my opinion.

 

Where is the fuel lever buffer sensor? And was your fuel pump relay acting up as well... This is the most mysterious issue I have ever had with a truck and I tried searching the web for hours to see if I could find anyone with similar issues, and I cant..

 

My Blazer is a 97 so our components arent always located in the same place. They might be, but since i dont know for sure, I would check if I were you....I believe my buffer is located behing my glove box. I never saw it but thats where it is supposed to be. The cause of my problem wasnt the buffer, it was actually the fuel tank vapor pressure sensor. The only reason i mentioned the buffer is to let you know that the fuel gauge going ape **** could be a clue as to what is happening. I know on MY truck that the MAP, TPS, EGR, FTVP,Fuel level buffer and several others all use this common 5 vdc refence voltage. They are wired in parallel so if one shorts to ground it pulls the entire circuit voltage down. Find yourself a GOOD wiring diagram for your Blazer. It is your road map to solutions. I spent more time leaning over the wiring diagram than under the hood for my problem. Do you have access to a scanner that will read live data as you are going down the road? The live data is what gave me the clues i needed to find my problem. GOOD LUCK!

 

It's actually an O2 sensor code.
HelpWitBlazerPLZ, we have a section on DTCs (diagnostic trouble codes) right here.

 

I finally have found an answer to my problem in another forum and I will be attempting to relace the Oil Pressure Switch today


My guess would be that the oil pressure sensor (i.e. fuel pump switch), if defective, may fail not only intermittantly, but could drop from the normal 12 volts to something less, thus causing relay chatter. The relay chatter is caused when the pick voltage is less than needed. The theory behind relays is that it takes more to pick a relay than hold the relay closed.

This is classic failure, imho.

The reason many mechanics and dealers fail to find this type of failure is that they are weak in the electrical skills necessary to troubleshoot electrical/electronic problems. Their skills are strong mechanically, but not in electrical theory (i.e. trace a ladder diagram, understand loop and nodal analysis to isolate a complex circuit loop, etc.).

 

Instead of spending the money and time of replacing the oil pressure switch, Why not jumper it out temporarily to see if it corrects the problem. I hate to see the look on your face if the Blazer continued to act up.