CEL flashing on downhill only Express 1500 4.3
October 27th, 2016, 11:16 PM
#1
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CEL flashing on downhill only Express 1500 4.3
Hi Guys I have a 2007 chevy express 1500 with 4.3L engine with 238,000 miles it runs great, i have recently been having this issue where when driving on freeways or highways and have a long downhill run the CEL will blink until the van is level again, it does not sputter or run rough just the light flashing and goes off soon as van levels out, does not do it on uphill just downhill, any ideas? wanted to check here before i take it to shop, thanks in advance for any help.
October 28th, 2016, 9:48 AM
#4
CF Senior Member
Could be several things hopefully, others can help, but here are the code descriptions
p0300-https://www.obd-codes.com/p0300
p0171-https://www.obd-codes.com/p0171
p0174-https://www.obd-codes.com/p0174
p0300-https://www.obd-codes.com/p0300
p0171-https://www.obd-codes.com/p0171
p0174-https://www.obd-codes.com/p0174
October 28th, 2016, 2:46 PM
#5
CF Monarch
My take is the 171, 174 is causing the 300 misfire. May be a dumb question, but is your gas tank full, part full, does it matter on the fuel level when you get this?
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October 28th, 2016, 9:07 PM
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It doesnt matter if the tamk is full or what level CEL light will still blink, probably the original fuel pump, dont know about fuel filter. didnt mention that sometimes the light will stay on then go off after about 50 miles of driving
October 28th, 2016, 11:50 PM
#9
One of the fixes/causes on those links was a faulty or dirty MAF sensor. When coasting down a hill you force more air than the engine demands....perhaps that is causing temporary fault. Try cleaning the MAf sensor.
October 29th, 2016, 10:46 AM
#10
check for things that lean out the fuel system on both banks.
view the fuel trim data at idle and 2500 rpm. if it is more than +10% all the time, the issue can be low fuel pressure, bad maf.
it the ft is adding at idle but normal(0 to 10%) at 2500, you have a vacuum leak anywhere from the air filter snorkel to the intake manifold.
the hard decell will accentuate a vacuum leak
view the fuel trim data at idle and 2500 rpm. if it is more than +10% all the time, the issue can be low fuel pressure, bad maf.
it the ft is adding at idle but normal(0 to 10%) at 2500, you have a vacuum leak anywhere from the air filter snorkel to the intake manifold.
the hard decell will accentuate a vacuum leak