intermittent engine problems
09-15-2009, 03:16 PM
#1
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Join Date: Aug 2006
Location: Fayetteville, GA
Posts: 649
intermittent engine problems
It seems like it runs fine for like 10-15 minutes then it begins idling rough, sometimes dying. Also, it sometimes throws up a SES light and dies immediately. I am currently getting the following codes...
16 lo-res fail
36 hi-res fail
41 est open
48 MAF system fail
51 EPROM/Flash Checksum Fail
I think it may be an opti but I dont know what the dtc 51 or 48 would have to do with it. Any advice would be appreciated. Thank you!
16 lo-res fail
36 hi-res fail
41 est open
48 MAF system fail
51 EPROM/Flash Checksum Fail
I think it may be an opti but I dont know what the dtc 51 or 48 would have to do with it. Any advice would be appreciated. Thank you!
09-15-2009, 04:03 PM
#2
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Join Date: Sep 2004
Posts: 0
A 51 is fatal and usually PCM. However there are certain voltage conditions that can "falsely" cause the PCM do to all sorts of weird things, 51 included.
First be sure the battery is in good shape and not sucking all the power from the charging system. Check the battery with everything turned off the battery should have 12.6 volts. While cranking the starter, the battery should never drop below 11 volts (obviously checking with someone's help). Once the engine is running, it should be at least 14 volts across the battery. Anything different and it has to be investigated.
Assuming that is ok, now check the output of the alternator for bad diodes. If the diodes are not filtering out the AC so to speak, it will cause weird things to the PCM. To do so set the DVM to AC and measure from the output terminal of the alternator to the negative battery terminal with the engine running. Any reading over 0.03 VAC is time to replace the alternator.
If that is ok, it's time to take your PCM to the an autovalue to have it reprogrammed. A defective PCM can show up there and it's not expensive either.
It's best to answer the problem concerning the 51 first since you don't know what other problems are being generated by a faulty PCM. I will tell you this, I have yet to see a faulty OBDI PCM
First be sure the battery is in good shape and not sucking all the power from the charging system. Check the battery with everything turned off the battery should have 12.6 volts. While cranking the starter, the battery should never drop below 11 volts (obviously checking with someone's help). Once the engine is running, it should be at least 14 volts across the battery. Anything different and it has to be investigated.
Assuming that is ok, now check the output of the alternator for bad diodes. If the diodes are not filtering out the AC so to speak, it will cause weird things to the PCM. To do so set the DVM to AC and measure from the output terminal of the alternator to the negative battery terminal with the engine running. Any reading over 0.03 VAC is time to replace the alternator.
If that is ok, it's time to take your PCM to the an autovalue to have it reprogrammed. A defective PCM can show up there and it's not expensive either.
It's best to answer the problem concerning the 51 first since you don't know what other problems are being generated by a faulty PCM. I will tell you this, I have yet to see a faulty OBDI PCM
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