Archived Engine off, key on, truck shows boost and oil pressure

[Weidner]

I have the truck at a dealer and it is showing boost and oil pressure with the engine off and key on through the ecm. I had codes for low voltage at apps, map and oil pres sensor set while I was working on it. It has little to no throttle response with the pedal, but runs fine using cruise control. He is not sure what is causing this. ANy thoughts?

 

[Marco]

The pressure sensors read absolute pressure. That means, even with the engine off the sensors still read the atmospheric pressure, about 15 psi.

Nothing wrong there.



Marco

 

[Weidner]

The Dodge tech thinks I got a bad apps from his parts department. He is going to try a new one in the am.



Marco- do you think a bad apps could cause the truck to have little to no pedal response, but work ok on cruise control (01 ETH) and also set cods for apps, map and oil pres. for low voltage? I think its either that or maybe a bad ECU. Maybe its just time for the catcher...

 

[Marco]

do you think a bad apps could cause the truck to have little to no pedal response, but work ok on cruise control (01 ETH) and also set cods for apps, map and oil pres. for low voltage?

I've never seen such a situation. Difficult to say but it COULD be the APPS.

I COULD also be the ECM.



Does the Wait to Start light work as usual? If it works, then the ECM is fine.



Marco

 

[Weidner]

Wait to start works perfect. They are going to try a new apps when it comes in today. I checked all the wires to the sensors from the ecm and all were fine, so hopefully its the apps.

 

[Marco]

Wait to start works perfect.

Then the ECM is OK.



Marco

 

[Kirwin]

Wait to start

Marco, Do you mean the 2 second bulb check? If not, how do you get the wait to start light to come on with engine temp >68 F? I'm just trying to understand if I have a future problem. Ken Irwin

 

[pwerwagn]

Are you sayin if your engine temp is >68* your wait to start light does not come on?

 

[KYLE4]

Mine always comes on no matter what temp it is outside it could be 100 f and it still come's on

 

[KYLE4]

My wait to start light always come's on no matter what temp it is

 

[Beast2B]

I think we're talking different situations: The WTS light comes on at the start of the sequence no matter what, every time you turn the key on, right? The WTS light comes on and stays on at lower ambient temps until the heaters warm up.

Are these results with the Edge box plugged in? I saw some weird values with my Comp on, I assumed it was the intercepted/modified signal from the MAP through the Edge box. I also fixed a stumbling/cutting out trouble by moving the ground wire for my Comp to the left fender where the battery neg attaches to the fender. Another post a week or two ago mentioned making a better ground for the ECM.

 

[Kirwin]

Yeah what he said

Beast3B You are correct. The lamp is turned on by the PCM for 2 seconds at the initial "key on" and then if temperature is below the set temperature, (that has changed several times since the 1989 diesel Ram was introduced) the lamp will stay on until the heaters turn off.



Marco, could you explain what you mean when you say the PCM is OK if the wait to start light works "as usual". Do you mean comes on for the 2 second bulb check, or comes on as it should times out and then turns off due to low temperature? Is there a way to fool the PCM into thinking it is cold enough to energize the heaters? Thanks Ken Irwin

 

[Marco]

Marco, could you explain what you mean when you say the PCM is OK if the wait to start light works "as usual". Do you mean comes on for the 2 second bulb check, or comes on as it should times out and then turns off due to low temperature? Is there a way to fool the PCM into thinking it is cold enough to energize the heaters? Thanks Ken Irwin

Kirwin,

that's the ECM we're talking about... Typo?

During the 2 seconds which we normally refer to as a bulb check the ECM runs in reality a self test. The WTSL works for those 2 sec? The ECM has found itself to be fine... No WTSL, looong WTSL, very short WTSL are all symptoms of an bad ECM. That's the reason for my question about the WTSL.



When the temperature is cold enough ( below 63°F for the 24V) then the grid's are turned on by the ECM thus the longer WTSL. The ECM reads the "ambient" temperature through the IAT. The IAT has a given resistance for a given temp. If you want to fool the ECM you can use a simple potentiometer.



Marco

 

[Weidner]

Dodge tech found the apps was fine, after testing it with yet a third unit. He called STAR they put him through a flow chart and decided I need a ECM. Another few days to wait for the new ECM to get in then let him program and install it. I will keep you posted. Oh, by the way, is that ECM made of gold? $$$ Merry Christmas truck. And I asked about the MAP showing pressure with key on being normal with the atmospheric, mine he said, was showing too much pressure for the normal atmospheric pressure.

 

[Marco]

I still don't believe that's the ECM... Anyway, what do I know... :-laf



How much do they want for a new ECM?



Marco

 

[GIT-R-DONE]

Dodge tech found the apps was fine, after testing it with yet a third unit. He called STAR they put him through a flow chart and decided I need a ECM. Another few days to wait for the new ECM to get in then let him program and install it. I will keep you posted. Oh, by the way, is that ECM made of gold? $$$ Merry Christmas truck. And I asked about the MAP showing pressure with key on being normal with the atmospheric, mine he said, was showing too much pressure for the normal atmospheric pressure.

See if the dealer will let you keep the old ecm, I always wondered if they would let yo keep your truck parts. You should be able to keep it, after all, you paid for it... ... .



Marco, last time I checked at the dealer, these ECM's were Very expensive, I think over $ 1000 . ( one Thousand )



Weidner, keep us posted.....

 

[Marco]

WOW over 1K for an ECM????



Bob Wagner can get him an ECM with the CaTCHER for much less... .



Marco

 

[Kirwin]

PCM vs ECM

Marco, I'm not sure which trucks use a PCM and which trucks use an ECM. I have one of each generation and I thought that my 97 had a PCM and the 91 vintage with the 4 speed auto and intercoller had a PCM and the 03 had a ECM. Is this correct? I'm just trying to understand you that having a sucessfull WTS light bulb check cycle indicates that the PCM/ECM has performed a sucessful self test. If that is what you mean, thanks. If I missunderstood what you meant please correct me.

 

[Weidner]

My price on the ECM is a little different, I work for another car line dealer that is owned by the same family that owns the Dodge dealer, so they give me a break. I have to give them $575 for one, then they charge me 1/2 price on the labor. It does not look like the ECM to me either, but thats why I have it at the dealer, so they can test parts on it. I already gave it a MAP and a APPS, and tested the harness to the ECM. I can't wait to see what fixes this thing! I just can't figure out how the cruise control can work to maintain speed and resume works great for power, but the throttle gives little to no response. I think the PCM operates the cruise and the ECM operates the accelration, and maybe thats why it needs an ECM.

 

[AKAMAC]

Your CC is controled via the ecm. The autos still had the vacuum servo.