Service Engine Soon light
DCSwartz
04-01-2007, 07:33 AM
We have a 2000 GMC Savana 1500 Hightop Conversion Van with a 5.7L engine & automatic transmission with 113K mile.
I am trying to understand a ‘Service Engine Soon’ light. It seems to be an emissions issue.
Maybe I should start at the beginning. It all started at about 100K mile with a gas gauge malfunction. I finally purchased a sender unit from Rockauto. Dropping tank and replacing it fixed the fuel gauge. Then while on a trip the fuel pump quite working. I replaced the fuel pump with an Autozone part. (Little choice at the time.) Found the pump was not the issue it was the connector in front of the emissions evaporator canister on the front of fuel tank. With a good pair of eyes it could be seen the spring part of the pin and socket had lost its spring. The fuel pump power was subject to intermittent interruptions. I finally (on the connector) cut the power wires for the fuel pump, by passed the connector and twisted the bare wires together with a wire nut. To keep moister out, I used RTV on the nuts. A thousand mile or so down the road the ‘Service Engine Soon’ light came on. DTC (Diagnostic Trouble Code) Error P0452 & P0446 were first noted at the local Autozone store. I tightened up the hose clamp on the fuel tank fill line to resolve these errors. I blamed the sloppy mechanic (me). A while down the road P0453 became an issue.
I temporarily connected a hand pump to the Evaporator Canister Vent line and eventually pumped the system down to about 3” of vacuum. You could hear the gas cap hissing air into the tank. The vacuum held at a little under 3”. Seemed like a good tight system for a motor vehicle.
Then I swapped out the new pump with the old thinking maybe the fuel tank pressure sensor had intermittent issues. A misfire developed. The engine service light then went to flashing. The owner’s manual said I had a misfire. I could tell that before the computer did and I am hard of hearing.
The little lady wanted the new pump re-installed. Some how, they know best. While the tank was down I closely inspected all lines for condition and who goes where. I also applied voltage to both fuel tank sensors and compared signals. They seemed quite similar. I re-installed new pump. Nothing had changed.
I needed more input, I purchased an ElmScan 5 USB with PCMSCAN software from TunerTools.com. They shipped Priority Mail and I got it in less than 4 days of ordering. After resolving learning curve issues, the misfire was fixed by replacing a less than a year old spark plug.
The DTC code now is back to P0452. But the new toy gives me little information on the emissions system. That seems like a rip off. From what I read, I guess, I should blame GMC not ElmScan & PCMSCAN.
I have taken a trip to a big library and spent time photographing pages out of their Mitchell Repair, Engine Performance manual for 2000. I found a very simple picture of my emissions system. A small piece of added understanding: The drawing leaves out a very self evident check valve that must be in the vent line or evaporator canister. If there is a positive pressure in the gas tank it does not vent to atmosphere with the engine off. Means to me there is a check valve preventing the venting of the fuel tank pressure.
I felt the need to know what the computer inputs and outputs were seeing and doing. Since my OBDII was not going to tell me I located the Evaporative Emissions Canister Purge Valve, Evaporative Emission Canister Vent Valve, Fuel Tank Pressure Sensor signals, & Evaporative Canister Purge Hose Service Port. I connected a gauge, DVM and laptop to everything at one time and took a 5 plus mile test drive on a cold engine, twice. No DTC yet.
The only real strange thing I’ve seen is something I have not seen. There has been no indication that the Evaporative Emission Canister Vent Valve ever closes. My concern is when should, it close by energizing the solenoid. During it’s self diagnostics? Maybe a longer test drive is necessary.
In between test drives I repositioned the fuel system return line to it’s more original position (I think). Nothing has been fixed at this point.
I then removed the connectors from the computer and did a Continuity check of the Vent valve wire to the computer. I found it and I added a very small test point wire when I reinserted the computer connector. I also removed the mechanical vacuum gauge from the Service Port. On the next test drive surprise, the Vent valve really closed. You could tell by watching the gas tank pressure sensor voltages. The sensor voltage went above 1.5 volts while driving.
On a longer test drive a positive pressure developed in the gas tank after the engine got good and warmed up. The Purge Valve voltage indicated it was opening to vacuum out the evaporator canister but the Fuel tank sensor indicated a positive pressure in the gas tank. Pressing the Service Port relief valve caused the tank pressure to go to atmosphere. I suspected the Canister Purge Valve was not opening when hot. Tried a lubrication technique on the valve. It seemed to help.
Shortly there after the Fuel Tank Pressure Sensor signal went to 5 volts and stayed there. Swapped that out and things looked great. After a week without any ‘Service Engine Soon’ light, I took a peek at the OBDII again and the Evaporator states was still incomplete. Meaning it would be on sooner or later? Also the emissions testing folks would fail my vehicle if given the chance.
I took a short test drive, looking just at the Fuel tank pressure sensor. Things looked good until I parked the car and the fuel tank pressure went positive and would not go near or below atmospheric pressure. It seemed as though the Canister Purge Valve was not opening again. I installed a new one.
With another short test drive there was no indication of a positive pressure in the Fuel Tank. After several days I took another look at the system monitors via the OBDII and all the supported monitors were complete. I think it can be called fixed, OK to have inspection done.
I am trying to understand a ‘Service Engine Soon’ light. It seems to be an emissions issue.
Maybe I should start at the beginning. It all started at about 100K mile with a gas gauge malfunction. I finally purchased a sender unit from Rockauto. Dropping tank and replacing it fixed the fuel gauge. Then while on a trip the fuel pump quite working. I replaced the fuel pump with an Autozone part. (Little choice at the time.) Found the pump was not the issue it was the connector in front of the emissions evaporator canister on the front of fuel tank. With a good pair of eyes it could be seen the spring part of the pin and socket had lost its spring. The fuel pump power was subject to intermittent interruptions. I finally (on the connector) cut the power wires for the fuel pump, by passed the connector and twisted the bare wires together with a wire nut. To keep moister out, I used RTV on the nuts. A thousand mile or so down the road the ‘Service Engine Soon’ light came on. DTC (Diagnostic Trouble Code) Error P0452 & P0446 were first noted at the local Autozone store. I tightened up the hose clamp on the fuel tank fill line to resolve these errors. I blamed the sloppy mechanic (me). A while down the road P0453 became an issue.
I temporarily connected a hand pump to the Evaporator Canister Vent line and eventually pumped the system down to about 3” of vacuum. You could hear the gas cap hissing air into the tank. The vacuum held at a little under 3”. Seemed like a good tight system for a motor vehicle.
Then I swapped out the new pump with the old thinking maybe the fuel tank pressure sensor had intermittent issues. A misfire developed. The engine service light then went to flashing. The owner’s manual said I had a misfire. I could tell that before the computer did and I am hard of hearing.
The little lady wanted the new pump re-installed. Some how, they know best. While the tank was down I closely inspected all lines for condition and who goes where. I also applied voltage to both fuel tank sensors and compared signals. They seemed quite similar. I re-installed new pump. Nothing had changed.
I needed more input, I purchased an ElmScan 5 USB with PCMSCAN software from TunerTools.com. They shipped Priority Mail and I got it in less than 4 days of ordering. After resolving learning curve issues, the misfire was fixed by replacing a less than a year old spark plug.
The DTC code now is back to P0452. But the new toy gives me little information on the emissions system. That seems like a rip off. From what I read, I guess, I should blame GMC not ElmScan & PCMSCAN.
I have taken a trip to a big library and spent time photographing pages out of their Mitchell Repair, Engine Performance manual for 2000. I found a very simple picture of my emissions system. A small piece of added understanding: The drawing leaves out a very self evident check valve that must be in the vent line or evaporator canister. If there is a positive pressure in the gas tank it does not vent to atmosphere with the engine off. Means to me there is a check valve preventing the venting of the fuel tank pressure.
I felt the need to know what the computer inputs and outputs were seeing and doing. Since my OBDII was not going to tell me I located the Evaporative Emissions Canister Purge Valve, Evaporative Emission Canister Vent Valve, Fuel Tank Pressure Sensor signals, & Evaporative Canister Purge Hose Service Port. I connected a gauge, DVM and laptop to everything at one time and took a 5 plus mile test drive on a cold engine, twice. No DTC yet.
The only real strange thing I’ve seen is something I have not seen. There has been no indication that the Evaporative Emission Canister Vent Valve ever closes. My concern is when should, it close by energizing the solenoid. During it’s self diagnostics? Maybe a longer test drive is necessary.
In between test drives I repositioned the fuel system return line to it’s more original position (I think). Nothing has been fixed at this point.
I then removed the connectors from the computer and did a Continuity check of the Vent valve wire to the computer. I found it and I added a very small test point wire when I reinserted the computer connector. I also removed the mechanical vacuum gauge from the Service Port. On the next test drive surprise, the Vent valve really closed. You could tell by watching the gas tank pressure sensor voltages. The sensor voltage went above 1.5 volts while driving.
On a longer test drive a positive pressure developed in the gas tank after the engine got good and warmed up. The Purge Valve voltage indicated it was opening to vacuum out the evaporator canister but the Fuel tank sensor indicated a positive pressure in the gas tank. Pressing the Service Port relief valve caused the tank pressure to go to atmosphere. I suspected the Canister Purge Valve was not opening when hot. Tried a lubrication technique on the valve. It seemed to help.
Shortly there after the Fuel Tank Pressure Sensor signal went to 5 volts and stayed there. Swapped that out and things looked great. After a week without any ‘Service Engine Soon’ light, I took a peek at the OBDII again and the Evaporator states was still incomplete. Meaning it would be on sooner or later? Also the emissions testing folks would fail my vehicle if given the chance.
I took a short test drive, looking just at the Fuel tank pressure sensor. Things looked good until I parked the car and the fuel tank pressure went positive and would not go near or below atmospheric pressure. It seemed as though the Canister Purge Valve was not opening again. I installed a new one.
With another short test drive there was no indication of a positive pressure in the Fuel Tank. After several days I took another look at the system monitors via the OBDII and all the supported monitors were complete. I think it can be called fixed, OK to have inspection done.
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