Thread: 2004 comp g

Reduce engine power and low fuel light after putting 10 gallons of fuel in the car and blowing the fuel pump fuse. Is this cause the map or maf sensor be going out?

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Originally Posted by Fivefingerdeathpunch

REP triggers an engine code.

Pull the code and diag the problem from there. The MAF and MAP alone won't blow a fuel pump fuse.

I just went and bought a engine scan tool and it pulled up a barometric pressure sensor performance code and throttle body code. I'm just wanting to know what is a barometric pressure sensor is bud

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Originally Posted by pickettjarred

I just went and bought a engine scan tool and it pulled up a barometric pressure sensor performance code and throttle body code. I'm just wanting to know what is a barometric pressure sensor is bud

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Usually when you see the barometric code, it's telling you that you have a vacuum leak or other issue. If you can read the map sensor values, you can verify this, or you can observe the voltage with a multimeter between 0 and 5v. What throttle body code are you referring to?

I would either try the vacuum leak test with carb cleaner, propane, or best case, see my thread on vacuum smoke leak detector in the how -to section. My money is on vacuum leak. How's it run at idle? And can you read short term and long term fuel trims. Positive ltft would indicate vacuum leak.

Have you checked the fuel pressure key in, engine off and when running?

Originally Posted by wstefan20

Usually when you see the barometric code, it's telling you that you have a vacuum leak or other issue. If you can read the map sensor values, you can verify this, or you can observe the voltage with a multimeter between 0 and 5v. What throttle body code are you referring to?

P0068 is the code and I got a p0069 code also

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Originally Posted by wstefan20

I would either try the vacuum leak test with carb cleaner, propane, or best case, see my thread on vacuum smoke leak detector in the how -to section. My money is on vacuum leak. How's it run at idle? And can you read short term and long term fuel trims. Positive ltft would indicate vacuum leak.

Have you checked the fuel pressure key in, engine off and when running?

And it runs fine. After a minute of it running it'll drop the fuel level to empty and continue to run like a charm. It had a reduce engine power light come on my guage and it'll loose everything if I drive a quarter of a mile

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I think you might have two separate problems. The codes you have usually indicate a vacuum leak, along with the reduced power, and the gauge sounds like a bad fuel level sensor which could be why the engine is turning off, but I don't know enough about the newer gps computer system to say for sure. Just to be safe, I'd still rent the fuel pressure gauge (easiest thing in the world, there's a Schrader valve where you hook the gauge up) and take a reading with key on engine off, running, and throttle snap just to rule out the fuel pump. I'll see if I can't find a how to diag for that issue.

As for the map codes, I'd check for vacuum leaks using the methods in my prior posts. There's good you tube videos on all the methods.

So the gauge will read empty when the gauge ground is disconnected. Again, I'd test the fuel pressure. Not sure if there's an easy way to test the sending unit on the 04+ models without dropping the tank, but there's lots of videos on how to test this and your fuel pump. Hopefully the 04+ guys chime in on that. Without seeing it though, my gut feeling is that there is either a bad section of wire, corrosion, and most likely, the ground for the fuel pump. I'd start by checking the pump ground for corrosion.

Originally Posted by wstefan20

So the gauge will read empty when the gauge ground is disconnected. Again, I'd test the fuel pressure. Not sure if there's an easy way to test the sending unit on the 04+ models without dropping the tank, but there's lots of videos on how to test this and your fuel pump. Hopefully the 04+ guys chime in on that. Without seeing it though, my gut feeling is that there is either a bad section of wire, corrosion, and most likely, the ground for the fuel pump. I'd start by checking the pump ground for corrosion.

I appreciate all the info bud. I'm about to the point of buying a donor motor and building the thing.

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Originally Posted by pickettjarred

I appreciate all the info bud. I'm about to the point of buying a donor motor and building the thing.

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I understand troubleshooting can be annoying, but If this is a fuel pump or grounding issue, you'll be throwing your money away because you'll have the same issue even if you went back in time and grabbed a brand new engine off the assembly line. Trust me, I used to be a parts swapper, and I've wasted a lot of money and time versus me not taking the time to figure the real problem out. I hope I'm not coming off too harsh, my only intention is to help you not make the mistakes i have. In the end, it's your choice, and I wish you luck either way! We're always here when you need help.

Originally Posted by wstefan20

I understand troubleshooting can be annoying, but If this is a fuel pump or grounding issue, you'll be throwing your money away because you'll have the same issue even if you went back in time and grabbed a brand new engine off the assembly line. Trust me, I used to be a parts swapper, and I've wasted a lot of money and time versus me not taking the time to figure the real problem out. I hope I'm not coming off too harsh, my only intention is to help you not make the mistakes i have. In the end, it's your choice, and I wish you luck either way! We're always here when you need help.

I'm just worried this motor is about to blow up. I've had a lot of problems with it and just tired of it. plus side I'm wanting to go with a turbo application and to make the next motor last I'm wanting to build it.

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Ok so lets first diagnose the car. There is a need to verify the fuel system. As these are returnless always verify everything. As stated you could throw brand new off the line wngine in and if parts hanging on it are junk your pissing in the wind.
P0068 means that the Powertrain Control Module (PCM) has detected an excessive degree of variation in the input voltage signal from the throttle position sensor (TPS) as compared with voltage input signals from the mass air flow (MAF) sensor and the manifold air pressure (MAP) sensor. The PCM reads and calculates these individual engine drivability sensor signals and then compares them to help develop fuel delivery and ignition timing strategy. The PCM also utilizes this information to ensure that the fuel-to-air ratio remains constant, controllable, and within acceptable limitations. If the detected voltage values of these three sensors (triangulated) fail to coincide with programmed desired parameters, over a specific period of time or engine revolutions, a diagnostic trouble code will be stored and a malfunction indicator lamp will likely be illuminated.The most frequent contributors to this code being set are large vacuum leaks as a result of cracked, broken, or otherwise collapsed vacuum lines and hoses. Other sources of vacuum leaks include defective intake and throttle body gaskets, EGR valve and gasket malfunctions, and vacuum operated component (brake boosters, etc.) defects. Other possible causes could include a cracked or disconnected air intake pipe, clogged air filter, a faulty TPS, MAF, and/or MAP sensor, or a defective PCM.

P0069 The manifold absolute pressure (MAP) sensor is used to measure engine load. The powertrain control module (PCM) sends the MAP sensor a reference voltage and the sensor varies the voltage according to manifold vacuum. The PCM then uses this information to adjust ignition timing and fuel delivery.
Vacuum and pressure are inversely proportional (when vacuum goes up, pressure goes down). Because of this, the MAP sensor is able to measure the pressure in the intake manifold to gauge vacuum. Manifold vacuum is a good indicator of engine load. With the engine off, manifold pressure and atmospheric (barometric) pressure are the same. With the engine running, the movement of the pistons and restriction of the throttle plates create vacuum (reduce pressure). When the engine is under heavy load at wide open throttle (WOT), vacuum is nearly zero. At this time, engine pressure and atmospheric pressure are almost the same.

Depending on the elevation, barometric pressure is usually between 28 to 31 inches of mercury (Hg). By comparison, engine vacuum at sea level is between 17-22 in-Hg. This drops approximately 1 in-Hg for every 1000 ft. of elevation. On some vehicles, when the engine is first started, the PCM looks at the MAP sensor to determine barometric pressure. There are other vehicles, however, that use a dedicated BARO sensor. Others still use a combination BMAP sensor.

There are two types of MAP sensors: analog and frequency. The analog type uses a diaphragm and is connected to the intake manifold by a vacuum line. The sensor monitors the movement of the diaphragm and sends a corresponding analog signal back to the PCM. This type of sensor will have three wires: reference, signal and ground. The other type of MAP sensor is the digital, or frequency type, which produces a digital voltage signal instead of an analog signal.

analog-map-sensor

A cut away of an analog MAP sensor

(Courtesy: autozone.com)

As was mentioned, some vehicles use an independent BARO sensor. These devices are designed to measure only barometric pressure. The BARO sensor is similar to the MAP sensor in design but is more sensitive to changes in atmospheric pressure.

The code P0069 stands for manifold pressure/barometric pressure correlation. The PCM compares BARO sensor and MAP readings at idle. If the difference between the two is greater than specified, the PCM will set a diagnostic trouble code (DTC).
MAP sensor circuit problem
BARO sensor circuit problem
Faulty MAP sensor
Faulty BARO sensor
Faulty PCM