Is there any way to diagnose the "Check Engine" light on my 98 F-150 without a diag tool? I remember some cars you can turn the ignition on and off a certain amount of times, and according to the amount of blinks, that's your code. It just came on this morning, and it's starting to worry me. Nothing's acting strange; it's running fine.

I would've searched, but, I can't seem to find the search option anymore...

 

i dont remember that trick your talking about with the ignition but If you live close to an Autozone they will check the codes for free. Hope that is helpful for you.

 

The trick was to use a jumper wire or paperclip to connect two of the terminals in the ALDL connector, then turn the key on, but not start it. It then would flash a series of codes. I bought a cheap code scanner ($129 at Advance)because I could never remember which terminals to jump to get it into diagnostic mode...
I just checked here: http://www.georgiasyty.com/aldl.htm
and it has a diagram of the ALDL connector and pin markings. You jump the A and B terminals- ground and diag. This is a very basic way to do this, as it flashes the check engine light to give you the codes. It's much easier to go to AutoZone or Advance and let them scan it free- it'll give you the code(s) and a short description.

Just be aware that it's giving you a code based on parameters, and that doesn't necessarily mean that replacing the part will solve the problem, since many of the subsystems work together to perform a task. The code is a head start on drilling down to the real problem. For instance, I got a P0401 code, which the short desc reads as insufficient EGR flow. Some folks would just start replacing EGR, Purge valve, control solenoide, and so on until they fixed it. I tested each of the components and found that they were all working within parameters, but something was still wrong- the light kept coming back after clearing it. Turned out that it wasn't a bad part after all, just carbon build up inside the EGR passage in the intake manifold, restricting the flow and throwing the P0401 code.

So, the code pointed me to the subsytem, but it was still up to me to pinpoint the culprit. Throwing parts into the subsystem that gave the code can get very very expensive. I also suggest that you search this entire site and the internet for more info before you do anything. This site alone has already saved me thousands!

Search posts for EGR, you'll see what i mean.

Oh, and be wary of Ford's 'Streamline Diagnosis'. It's not always correct- just saves Ford time up front on service work. But it doesn't always solve the problem! That's not much of a diagnosis if you ask me... in the case of my EGR, it was way off base and cost me money to replace the DPFE sensor that was working fine .

Good luck.
~Rob

 

Ok, went over to my local autozone, and had him run a diagnostic.

The error code was P0402, which comes up to "Exhaust Gas Recirculation Flow Excessive Detected".

Now, he cleared the code (which I found out he shouldn't have done from the manager), and ran up a price sheet for a EGR sensor and EGR regulator. About 120$'s total with tax. What I did was take the connections off my current EGR sensor, clean the contacts, and tapped the sensor a few times (hey, I've done that before and fixed electrical problems, so, I figure it couldn't hurt). I decided not to buy and replace anything, and see if that fixed it.

So far, the check engine light hasn't come back on. Here are my questions now.

How long does it take for OBDII to pick up the faulty EGR sensor/regulator if it's still defective?

Would running my gas tank low a couple of times in a row (not to the point of running out of gas, but, running on fumes to the gas station) cause anything funny like this to happen? I noticed after I left autozone and went to fuel up, it gave the me lower-octane kind of hesitation and noise which it's never done before. I normally fuel up with 86 octane, and I put in 90 octane at the pump. Driving it back to work, I gunned it a few times to check for hesitation and see if I might have just got some bad fuel from the bottem of the tank, and by the time I got to work, I couldn't tell any hesitation or low octane fuel noises.

Thoughts?

 

Ok, an update.

The check engine light DID come on again yesterday afternoon, so, I'll be calling the local wrecking yards on prices for an EGR sensor and start from there.

 

I wouldn't do that until you clean out the throtle body... I have been chasing the 401 code for months. Replaced all egr parts with the exception of the PCM. Still have the low flow code, check the simple stuff first, gaskets are a whole 10-15 to see if this could solve the issue. good luck

 

<TABLE cellSpacing=0 cellPadding=3 border=1><TBODY><TR><TD vAlign=top align=left>P0402 - EGR Flow Excessive Detected </TD><TD vAlign=top align=left>The EGR system is monitored for undesired EGR flow during idle. The EGR monitor looks at the DPF EGR signal at idle and compares it to the stored signal measured during key ON and engine OFF. The test fails when the signal at idle is greater than at key ON engine OFF by a calibrated amount. </TD><TD vAlign=top align=left>

• EGR valve stuck open
• Plugged EGR vacuum regulator solenoid vent
• Plugged EGR tube
• Slow responding D.P.F. EGR sensor
• Damaged DPF EGR sensor
• Improper vacuum hose connection
• Plugged vacuum hoses
• EGRVR circuit shorted to ground
• Damaged EGR vacuum regulator solenoid
• Damaged PCM

</TD><TD vAlign=top align=left>A DPFEGR PID reading that is greater at idle than during key ON and engine OFF by 0.5 volt or a rough engine idle, may indicate a hard fault.</TD></TR></TBODY></TABLE>




The switches can be tested for voltages, If you have a hand vacuum pump or you can place a piece of vacuum tubing on the componet and draw a suction with your mouth, then hold it with your tongue.

If you need any of the voltages for the egr componets let me know. I'd check the vacuum lines first. The EGR system vacuum diagram is in the engine compartment. Never just start swapping parts. It is easy to test the componets and verify if they work or not in a couple minutes with a multi meter.

 

Notice in the right hand box it says "if you have a rough idle or if the voltage is more or less then a half of volt difference from key on, no start, then at idle" this can produce the fault also.

 

Thanks for all the hints, guys. I'll give the sensor a look-see this weekend with my voltmeter and see what it gives.