Ignition On with Sensor's Unplugged

[Alan Reagan]

I fessed up on another post, but though I'd post a single here with a tip for anyone else that may be mentally challenged like myself. DON'T ever turn the ignition switch to the 'on' position while you have a sensor disconnected or it will set a fault code that the almighty can't even clear without a DRB scan tool. I inadvertently did it and a fault code was set. I thought disconnecting the batteries would clear it. Nope. I was doing a little work on the ride, it started raining, I let the windows up. BAM, code set. Dealer cleared it though and all is well.

 

[B.G. Smith]

Code

Don't feel bad, I did the same thing, almost. I tried the battery disconnect(all night) didn't work. I cycled the switch on-off, on-off, on-off then left on and the check engine light went out?????? bg

 

[Alan Reagan]

After so many cycles (mine was three, I believe) the light went out. However, the fault was still set. It had to be cleared by the dealer. Yours will be the same way. I think as soon as the software determines the fault no longer exists, the light is extinguished but the fault is stored until cleared by the scan tool. I noticed, too, that disconnecting the batteries (multiple times for extended periods) didn't clear my radio/clock or anything on the computer.

 

[B.G. Smith]

Code

Mine was the manifold pressure switch, will it affect the performance of the engine if it is not reset. I can't tell any difference in the way it runs. bg

 

[Alan Reagan]

The error, unless it is an input to put the engine in the limp home mode shouldn't affect engine performance. The ECM should still be reading the correct input from the MAP, IAT or other sensors. However, the error, until cleared remains stored in memory and the next time a DRB is connected, it may read that you MAP voltage is too high or low. At that point the connector voltage will be checked, unplugged from the sensor and if the voltage is OK, the technician would tell you that the MAP sensor needs replacing. Therefore, if you are in for service, they need to reset the faults, start the engine, shut it down and then check for faults with the DRB. That way you don't replace anything that's not broke.

 

[John Berger]

Me, too

I did that too, Alan. The check engine light stayed on, but cleared after I cycled the ignition a couple of times. I was undoing the EZ Box and didn't think. DOH!!! I'll get it cleared sometime down the road.

 

[Todd T]

you can sometimes clear freeze frame codes (permanent) by completing three full drive cycles. what is a drive cycle you ask... its not just disconnecting the negative battery cable for a minute or overnight. here is the drive cycle procedure for our trucks.



To perform an OBDII Driving cycle do the following:

1.

Cold Start. In order to be classified as a cold start the engine coolant temperature must be below 50°C (122°F) and within 6°C (11°F) of the ambient air temperature at startup. Do not leave the key on prior to the cold start or the heated oxygen sensor diagnostic may not run.

2.

Idle. The engine must be run for two and a half minutes with the air conditioner on and rear defroster on. The more electrical load you can apply the better. This will test the O2 heater, Passive Air, Purge "No Flow", Misfire and if closed loop is achieved, Fuel Trim.

3.

Accelerate. Turn off the air conditioner and all the other loads and apply half throttle until 88km/hr (55mph) is reached. During this time the Misfire, Fuel Trim, and Purge Flow diagnostics will be performed.

4.

Hold Steady Speed. Hold a steady speed of 88km/hr (55mph) for 3 minutes. During this time the O2 response, air Intrusive, EGR, Purge, Misfire, and Fuel Trim diagnostics will be performed.

5.

Decelerate. Let off the accelerator pedal. Do not shift, touch the brake or clutch. It is important to let the vehicle coast along gradually slowing down to 32km/hr (20 mph). During this time the EGR, Purge and Fuel Trim diagnostics will be performed.

6.

Accelerate. Accelerate at 3/4 throttle until 88-96 km/hr (55-60mph). This will perform the same diagnostics as in step 3.

7.

Hold Steady Speed. Hold a steady speed of 88km/hr (55mph) for five minutes. During this time, in addition to the diagnostics performed in step 4, the catalyst monitor diagnostics will be performed. If the catalyst is marginal or the battery has been disconnected, it may take 5 complete driving cycles to determine the state of the catalyst.

8.

Decelerate. This will perform the same diagnostics as in step 5. Again, don't press the clutch or brakes or shift gears.



after doing this three times the PCM "May" clear the codes itself without having to take it to a dealer. what is important to note here is that if you pull the codes and fix the problem, or think so anyway. the only true way to tell is to clear the codes and go through at least one full drive cycle, and make sure they dont come back. then you can be sure its fixed. that doesnt mean just start it up in the driveway and check for a light. drive it a few days to be sure.

 

[Alan Reagan]

Thanks, Todd. That's a lot of work. What I need is one of those scan tools but I won't pay the $2500 for it. I wonder if the Cummins Quick Chek software for the Palm Pilot will clear the engine codes.

 

[Todd T]

Alan, and others,



another thing i did was ran a jumper from my power seat fuse lacation to the window fuse location and wired the windows fuse to the jumper. that way my windows stay hot all the time, key in or out, on or off, the windows always work.

 

[Ladders]

Codes...

HHMMMM... if I gots this right, just before you goto a dlr (?) remove the IAT (or MAP or ??) connector, turn on ing = set code, reconnect wire(s), get dlr to replace IAT under warranty!!! Just might have tooo.....



SOTSU!!

\\BF//

 

[Alan Reagan]

Ben, You are smarter than the average bear . What you said is correct.