My college son just called and says he getting an intermittant Eng Chk Light on his 97 Corolla, 81k miles. I told him to check the gas cap,..change the air filter, and get an oil change. If it still continues what should we do next,..any engine gurus please,..? thanks

have him run it by AutoZone, they will scan the code for free

or you can take a magic marker and put a check mark on the valve cover ....

The autozone reader will only read the code when the light is on. Will not pull it up if the light is not on at the time he takes it to them

Take it to a Toyota dealer or a good automotive repair shop and have them hook it up and see what codes come up. They will probably charge you one hour of labor, but I have had more than one bad experience with autozone and their "technicians" with their code readers.

My guess..............O2 sensor........Assuming plugs, wires, cap, and rotor are good.

I have auto zone read my codes, then search them on the internet to find the problem. I would save your money and not by anything until you find out what the code is.

A common problem is the gas cap is not holding a vacuum. But run the code before you buy anything.

Jim, get the code then I will try and figure it out for ya.

Unless they got new coad readers it should pull the code from memory. they can also run the code on there computer and tell you what it is.

Ronnie, I have a P0526 on my 04 GMC envoy..whats that and don't just say "fan sensor circuit"--

Kingdad101 it is usually a bad fan clutch,my daughter just had hers replaced,it was not locking up like it is supposed to......hers was under warranty...thankfully...that is on the inline 6 cyl.

Here, more details:


DTC P0526

Circuit Description
The Powertrain Control Module (PCM) uses the cooling fan speed signal in order to determine the actual fan speed in relation to the desired fan speed. The PCM uses the cooling fan speed signal in order to reduce the cooling fan noise and in order to maintain the powertrain cooling requirements. The PCM supplies power and ground to the clutch hall effect sensor of the cooling fan clutch. The hall effect sensor returns a signal pulse through the speed signal circuit in response to the reluctor track, which is located inside the fan clutch. If during operation, the PCM detects a loss of the cooling fan speed signal, DTC P0526 will set.

Conditions for Running the DTC


The engine is running.
System voltage is greater than 8.5 volts.
Conditions for Setting the DTC


The PCM has detected a loss of cooling fan speed signal.
The above condition is present for at least 11 seconds.
Action Taken When the DTC Sets


The PCM will illuminate the Malfunction Indicator Lamp (MIL) during the second consecutive trip in which the diagnostic test has been run and failed.
The PCM will store the condition as Freeze Frame/Failure Records data.
The PCM commands the cooling fan to 100%.
Conditions for Clearing the MIL/DTC


The PCM turns OFF the Malfunction Indicator Lamp (MIL) after the third consecutive trip that the diagnostic test has run and passed.
Clear the DTC by using the Clear DTC Information function of the scan tool.
Diagnostic Aids


An inline connector could cause an intermittent DTC. Ensure to test for poor connections and pin retention at all inline connectors. Refer to system schematics for connectors and locations.
If the condition is not present, refer to Testing for Intermittent and Poor Connections.
Disconnect the harness connector of the cooling fan clutch from the shroud. Inspect the exposed wires between the harness connector and the tubing.
Inspect the cooling fan clutch harness in order to ensure that the clutch supply voltage circuit is not shorted to the following circuits:
The 5-volt reference circuit.
The cooling fan speed signal circuit.
The low reference circuit.
DTC P0526 will set if the engine is started without the drive belt ON.
Test Description
The numbers below refer to the step numbers on the diagnostic table.


Tests that the PCM receives a cooling fan speed signal through the cooling fan speed signal circuit. If answer to question is Yes, ensure to refer to all Diagnostic Aids.
Tests for the proper operation of the cooling fan clutch hall effect sensor. The voltage should fluctuate between 0 and 5 volts. If the voltage stays at 0 volts, the signal circuit is shorted to ground.
Tests for the proper operation of the 5-volt reference circuit and of the low reference circuit of the cooling fan clutch.

If you remember I had a time getting the fan clutch off to replace the water pump. After replacing the water pump ( I didn't replace the fan) after two weeks , the check light comes on amd may stay a day, and go out for some time, to only come on again..Guess I should have replaced the clutch the first time, But was trying to sace several hundred bucks...


fool4fishing --thanks for the overload.. - I don't have any ideal how to check those readings, but I appreciate your input..

lol.. i think you got all the info you needed