Trouble codes 159.512 on 93 explorer

[Gypsy81165]

I have been having trouble with my 93 Eddie Bauer explorer. I have had a mobile mechanic come out and try and figure this out. The truck would lose power like it was starving for gas. The temp gauge would go sky high. So long story short this is what has been replaced. Thermostat, radiator, o2 sensors, crank shaft sensor, MAF sensor. Now when this guy supposedly replaced the MAF sensor but when I drove the truck it hesitated. I got home discovered the sensor was not plugged in. Plugged it in the truck runs the same way but with the temp gauge staying steady.I went to do a diagnostic and discovered the check engine light had been unplugged also. I fixed the check engine light. Did a diagnostic with the truck running and came back with code 111, so all good there. With engine off key on got codes 159 and 512. Any input would be great. I need and love this old truck.

 

[natenkiki2004]

159 is for the MAF and 512 is for the KAM test failure. I'd imagine both of these were caused by either you or the mechanic. Disconnect the battery for 10 minutes, hook it up and drive it (if you can) for a day or two. Run the KOEO and KOER tests again and come back with the results.

Though I will say, losing power and the temp gauge going high... sounds like a head issue. Either gasket or cracking if it's an early 1993.

 

[Gypsy81165]

Well the temperature issue is good. It has not run high at all since the thermostat and radiator replacement. The truck ran great for about 2 weeks after the o2 sensors and crank shaft sensor were replaced. Then all of a sudden it started acting up again. Mechanic came to my work and supposedly replaced the maf sensor. I just think it is suspicious that the sensor was not plugged in and mysteriously the check engine light was taken out when it was there before he worked on it. Would new cover come with a MAF sensor? Why I ask is the same cover is on it. At this point I don't care if he took my money and ran I just want to fix my truck.

 

[Wolfie_85]

The MAF can come two ways: as an assembly that includes the metal tube with screens, or just the sensor itself. The "cover" is really just the casing of the sensor. If it's the same part, it won't look different at all, aside from being cleaner than the old one (unless it was a remanufactured unit or a different manufacturer.)

Another possibility is that he merely cleaned your MAF, not replacing it at all. I would ask to see the old MAF (or any other part, for that matter) that he replaced. I doubt he still has it, even if he is honest. But always ask to see the parts when having any replaced. If they refuse, something's up.

 

[Gypsy81165]

Thank you for the advice but at this point it doesn't matter what he did.

I did a diagnostic after I fixed the check engine light and came up with these codes. So I decided to disconnect the battery overnight and run the tests again. Same codes. Engine temp never ran high. Engine on code was 111. Engine off key on 159. 512. Could it be the pcm?

 

[MrShorty]

PCM is always a possibility. The difficulty is that diagnosing a bad PCM is either a "eliminate all other possibilities" or "guess and check".

My code list indicates that a CM 512 indicates a disruption in the keep alive memory (KAM) circuit -- possibly consistent with having disconnected the battery. I would be inclined to clear CM (by interrupting the test, not by disconnecting the battery, see any of our instruction pages for performing the KOEO test), then see if the CM 512 comes back.

KOEO 159 indicates some failure in the MAF circuit. KOEO codes are "hard faults" that indicate the fault exists at the time the test is performed (my code list indicates that a 159 cannot be a CM code, so I am assuming it is a KOEO code). Because the KOEO code is set while the engine is off, it is generally expected to be an electrical fault, though I find it interesting that you are not getting a KOER or CM MAF code. If you are certain the the MAF was replaced with a good unit, I would inspect the wiring between the PCM and MAF for any loose connections or broken connections.

 

[Gypsy81165]

Thank you I will check the wiring.

 

[FR-425]

KAM (keep alive memory) 512 failure is a PCM death code.

Fault codes are stored in KAM as well as drive cycle data. You will not get any codes from disconnecting the battery. Disconnecting the battery is a way to reset the PCM if you do not have a scan tool.

If the KAM is dead it may not erase and be "stuck" with error codes that have already been corrected. Probably why the mechanic just removed the CEL.

Your PCM is dead.

However try disconnecting again only this time touch the battery cables together to fully discharge all of the capacitors. It may actually clear the KAM and restore it.

If you continue to get 512 it's time for a PCM.