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Skyvisions
Skyvisions, ASE Certified Technician
Category: Toyota
Satisfied Customers: 12723
Experience:  Toyota Master Diagnostic
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1999 4runner: check engine light..mass air flow sensor..wiring harness

Resolved Question:

i have a 1999 4runner 3.4 l with150k that i just bought. check engine light was on, said mass air flow sensor so we replaced it. next code was knock sensor, replaced both when upper end was apart as well as the wiring harness for them. then the tcm code, replaced the tcm. light comes back on for about 200miles, then goes out on its own. truck passes computer inspection for nys today when light was out. after i pick up the truck and drive 2.5 miles the damn light comes on again. any ideas
Submitted: 2 years ago.
Category: Toyota
Expert:  Skyvisions replied 2 years ago.

Thank you for choosing JustAnswer and allowing me to help you resolve your Toyota questions!

 

Can you get me the engine code numbers that are currently set in the engine control computer? Most auto-parts stores like AutoZone do free engine code reads.

Customer: replied 2 years ago.
not now. took it to a toyota "master mech" at the dealer. said the code came back for knock sensor bank 1 and 2. The harness was replaced and all connections done with dielectrode grease. the light went out spontaneously after about 200 miles. but still should up in computer, however it just passed emissions inspection for ny when light was out. they reset the comp. light came back on in 2 miles. truck runs great though
Expert:  Skyvisions replied 2 years ago.
Are you saying that the dealership changed the knock sensors and the sub wire and the light still keeps coming back on and are telling you that the knock sensor codes are still setting in the system after they did the work?
Customer: replied 2 years ago.
No, I had my regular mech change them . the code keeps coming on. The toy master mech said it may be a connection since everything else is new. what perplexes me is the light went out on its own and then it past emissions inspection. it seems that every sensor we changed, the light would come on again with a new code. first the mass air flow, then knock sensor so we changed both, then light on again for knock and we replaced the harness,light again tcm which we replaced. light again, back to knock, light went out after about 200miles, past inspect. they cleared the codes and light back on within 2 miles. could it possibly be the computer. this truck runs great,so this is all very confusing
Expert:  Skyvisions replied 2 years ago.
Not likely the computer, can you get the codes currently set in the computer?
Customer: replied 2 years ago.
PO325
Expert:  Skyvisions replied 2 years ago.
This knock sensor code P0 325 indicates that the bank two knock sensor has an open or short circuit. Do you know where your mechanic purchased the knock sensors from? The only way this code can be set is if the knock sensor itself is not functioning is loose or the wiring between the knock sensor in the computer is open or shorted. You need to verify whether or not the input signal wire is shorting to ground. It's possible that the knock sensors probably weren't bad in the first place. If you're certain that they replace the little sub harness with a new one you can rule that out. However in some cases I have seen where the ground shielding which follows this tire wire the full length back to the computer could be shorting to the signal wire. This can usually be detected with a ohmmeter. If you disconnect the electrical connectors at the engine control computer then disconnect the connector at the knock sensors themselves and ohm test the center core wire to ground you should have no resistance to ground.
Skyvisions, ASE Certified Technician
Category: Toyota
Satisfied Customers: 12723
Experience: Toyota Master Diagnostic
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