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ECU for Jeep Cherokee



 
 
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  #11  
Old June 14th 05, 04:56 AM
Stephen Cowell
external usenet poster
 
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"reigelser" > wrote in message =
news
> It is an automatic transmission. What is the wiper return voltage? The =

other=20
> voltage I can measure on the TPS besides the ~200mV to ~4V?
> I check the message with an OBD Reader. P0123 I think is the number or =


> P0124, don't remember right now. Are you referring to the Check Engine =

Light=20
> flashing when you mension a 24 and a 15?


Yes... too cheap to get the OBD. '124' would correspond to
the '24'... TPS. =20

Start thinking about things like the ground wire
between the engine and the firewall.. this is a=20
known problem point. Doug has the right
idea... make sure all connections are clean
and tight.

Problem starting... to start an EFI vehicle, you
should keep your foot *off* the gas until the
vehicle has started... no need to touch the
gas until you take off. You're doing this,
right?

Has other maintenance been done recently?
Does the engine run smooth once it starts?
Describe what you have to do to get it
to start (i.e. grind long, grind twice, feather
throttle, etc.).

The TPS is basically a potentiometer, with three
wires going to it... supply, wiper, and ground. The supply
is a regulated voltage, sent by the computer and used
by the computer as a reference. If this is moving around,
the computer may have unfixable problems (blown regulator
pass transistor, etc.) or another sensor or connection may be
screwing up your TPS reading. The wiper voltage is the one that
changes as the throttle plate opens and closes... it should
track the position of the gas pedal steadily. The wiper
carries your 200mV to 4V.
__
Steve
..

Ads
  #12  
Old June 14th 05, 05:13 AM
Jerry Bransford
external usenet poster
 
Posts: n/a
Default

That may be but I would still place the ECU at the dead-end of any list
of likely culprits.

reigelser wrote:
> I replaced it allready and all voltages are fine in all ranges of motion of
> the TPS. I also tried to disable other parts of the electric system to see
> if there is an effect on the tps circuit, without success. The error won't
> clear and there is still an effect on the driving behavior.
> "Jerry Bransford" > wrote in message
> news:kAore.88$X71.85@fed1read07...
>
>>The TJ's ECU is known to be extremely reliable and just about
>>trouble-free. Have you already replaced the TPS and cleaned/reseated the
>>electrical connection that connects the ECU to the TPS? Bad TPSs are
>>easily replaced and far cheaper than replacing the ECU.
>>
>>Jerry
>>
>>reigelser wrote:
>>
>>>I need the ECU eventually because of a persistent TPS error. My mechanic
>>>troubleshooted it and thinks its probably the ECU. But he thinks there
>>>has to be some reprogramming to be done, because I tried one from the
>>>junk yard before he looked into it and nothing changed (same TPS error,
>>>same mileage). It's a 97 inline 6 Cherokee. It works, but it doesn't
>>>start at first try and it is not very smooth if you want to accelerate
>>>from 65 to 75 without a kickdown.
>>>
>>>"Stephen Cowell" > wrote in message
...
>>>
>>>"tim bur" > wrote in message
...
>>>
>>>
>>>>depends on the year starting in 04 all pcm,s are shipped with out
>>>>software and
>>>>it has to progammed by vin
>>>>now more salvage yard pcm swapping
>>>
>>>^^^^^^^
>>>
>>>One letter... how it changes things.
>>>Tim probably meant 'no'...
>>>__
>>>Steve
>>>.
>>>
>>>
>>>
>>>
>>>
>>>
>>>>reigelser wrote:
>>>>
>>>>
>>>>
>>>>>Hi,
>>>>>does anybody know, if there is some programming or calibration to be
>>>>>done if
>>>>>the engine control unit is replaced? Or do I just plug it in and thats
>>>>>it?
>>>>>Thanks for the advice.
>>>>>
>>>>>Jo
>>>>
>>>

>>--
>>Jerry Bransford
>>PP-ASEL N6TAY
>>See the Geezer Jeep at
>>http://members.cox.net/jerrypb/

>
>
>


--
Jerry Bransford
PP-ASEL N6TAY
See the Geezer Jeep at
http://members.cox.net/jerrypb/
  #13  
Old June 14th 05, 12:15 PM
reigelser
external usenet poster
 
Posts: n/a
Default

To start the car I have to crank it once for a short time. Even If I crank
longer it won't start. Then I turn the ignition off completely and start
again and runs immediately. There was no service done prior to the Check
engine light coming on. The wiper voltage seems very smooth and stable. I
haven't measured the supply voltage while having the engine running yet.
Everything else seems to run good: idle speed, kick down response. So would
you recommend an engine cleaning first (engine compartment wasn't cleaned in
a loooong time) and then a rework of the connectors?
Thanks for all of your advice.

"Stephen Cowell" > wrote in message
. ..

"reigelser" > wrote in message
news
> It is an automatic transmission. What is the wiper return voltage? The
> other
> voltage I can measure on the TPS besides the ~200mV to ~4V?
> I check the message with an OBD Reader. P0123 I think is the number or
> P0124, don't remember right now. Are you referring to the Check Engine
> Light
> flashing when you mension a 24 and a 15?


Yes... too cheap to get the OBD. '124' would correspond to
the '24'... TPS.

Start thinking about things like the ground wire
between the engine and the firewall.. this is a
known problem point. Doug has the right
idea... make sure all connections are clean
and tight.

Problem starting... to start an EFI vehicle, you
should keep your foot *off* the gas until the
vehicle has started... no need to touch the
gas until you take off. You're doing this,
right?

Has other maintenance been done recently?
Does the engine run smooth once it starts?
Describe what you have to do to get it
to start (i.e. grind long, grind twice, feather
throttle, etc.).

The TPS is basically a potentiometer, with three
wires going to it... supply, wiper, and ground. The supply
is a regulated voltage, sent by the computer and used
by the computer as a reference. If this is moving around,
the computer may have unfixable problems (blown regulator
pass transistor, etc.) or another sensor or connection may be
screwing up your TPS reading. The wiper voltage is the one that
changes as the throttle plate opens and closes... it should
track the position of the gas pedal steadily. The wiper
carries your 200mV to 4V.
__
Steve
..


  #14  
Old June 14th 05, 12:36 PM
DougW
external usenet poster
 
Posts: n/a
Default

reigelser did pass the time by typing:
> To start the car I have to crank it once for a short time. Even If I crank
> longer it won't start. Then I turn the ignition off completely and start
> again and runs immediately. There was no service done prior to the Check
> engine light coming on. The wiper voltage seems very smooth and stable. I
> haven't measured the supply voltage while having the engine running yet.
> Everything else seems to run good: idle speed, kick down response. So would
> you recommend an engine cleaning first (engine compartment wasn't cleaned in
> a loooong time) and then a rework of the connectors?
> Thanks for all of your advice.


What your describing may be a fuel delivery problem caused by either
the pressure regulator or check valve failing. Try this;

Turn the key on, but don't crank.
Turn the key off, wait a sec
Turn the key on, wait for the fuel pump to stop buzzing
Then try starting the engine.

If the engine fires up your problem is fuel pressure leaking
down. Diagnosing that further is slightly complicated but a cheap
fuel pressure gauge screwed into the fuel rail will indicate a leak
if it drops more than 5psi in an hour. The rail should hold pressure
for more than a day.

--
DougW


  #15  
Old June 14th 05, 03:39 PM
Stephen Cowell
external usenet poster
 
Posts: n/a
Default


"reigelser" > wrote in message =
. ..
> To start the car I have to crank it once for a short time. Even If I =

crank=20
> longer it won't start. Then I turn the ignition off completely and =

start=20
> again and runs immediately.=20


You may have more than one problem... try this
sometime... turn on the key, let the thing sit for
ten seconds, then crank... should go vroom.
It this is what you're seeing, you have a fuel
pressure retention problem... either the back-
check valve, or a leaky injector.

> There was no service done prior to the Check=20
> engine light coming on. The wiper voltage seems very smooth and =

stable. I=20
> haven't measured the supply voltage while having the engine running =

yet.=20
> Everything else seems to run good: idle speed, kick down response. So =

would=20
> you recommend an engine cleaning first (engine compartment wasn't =

cleaned in=20
> a loooong time) and then a rework of the connectors?
> Thanks for all of your advice.


I'm not that big of a believer in engine cleaning...
especially when trying to troubleshoot a problem.
Don't compound your problems right now.. sounds
to me like you've got more than one.

Is the big braided ground wire still connected
between the block and firewall? Look good?

Get some Caig ProGold contact cleaner (sold at Fry's)
and put some in the connector (both ends) for the
TPS... try again. I want to verify that you've cleared
the old ECU code, and it keeps popping a new one...
am I right? Does it pop immediately, or after normal
in-town driving, or only after exhibiting the symptoms
you describe at 60-70mph transition?
__
Steve
..


Lastly, you may have to go through several run/drive
cycles for the ECU to learn the curve of the new TPS...
  #16  
Old June 15th 05, 01:49 AM
tim bur
external usenet poster
 
Posts: n/a
Default

i have not seen in any posts giving a dtc for a tps issue
i have seen and replaced many a tps for a glitch in it's range causing all sorts of issues and some serious
testing with a drb and a dvom must take place
could be there is a couple of things going wrong though???
like the plug wires are shot. carbon on th valve thats causing a highway speed misfire and there was a tsb on
new valve springs for this issue and a weak battery
h



Stephen Cowell wrote:

> "reigelser" > wrote in message .. .
> > I need the ECU eventually because of a persistent TPS error. My mechanic
> > troubleshooted it and thinks its probably the ECU. But he thinks there has
> > to be some reprogramming to be done, because I tried one from the junk yard
> > before he looked into it and nothing changed (same TPS error, same mileage).
> > It's a 97 inline 6 Cherokee. It works, but it doesn't start at first try and
> > it is not very smooth if you want to accelerate from 65 to 75 without a
> > kickdown.

>
> So it only throws a 24 code? Do you have a manual
> or automatic transmission? Any aftermarket parts
> on the engine? It's never thrown a 15 (VSS)? That
> causes kickdown problems too...
>
> With the TPS, you can actually patch a digital
> voltmeter in and watch the voltage as you drive...
> won't hurt a thing. If the computer's bad, then
> you'd expect the +V to the TPS to fluctuate...
> if the TPS is bad, you'd expect the wiper return
> voltage to be wrong for the rpm, gear, etc.
> That's what I'd do next...
> __
> Steve
> .


  #17  
Old June 15th 05, 02:41 AM
reigelser
external usenet poster
 
Posts: n/a
Default

I just tried the proposed starting procedure. KeyOnEngineoff for 10sec and
then crank but no vroom. I needed a second try. When I turn the key I hear
the Fuel pump for approx 1sec (I believe its the fuel pump). With the engine
cold there is a little delay in the throttle response. Between Pushing the
throttle a bit and the revs coming up is a ~0.5sec delay. When I rev the
engine at 2000 and go of the Throttle it goes all the way down to ~300rpm
before it comes up to 800 again.
I checked the connectors (cleaned them with WD40) and the ground cable:
seem fine. Between engine block intake manifold and fire wall I measure ~0
Ohm resistance, so the ground seems good.
I can not reset the error right know, because I don't have the reader
available. But in the past I tried 50 times to reset the error and it is not
erasable. Sometimes the light goes off, but comes back on immediately.
Sometimes the device tells me, the error can't be erased.
At the moment the Check ENgine Light readt out tells me 12, 24, 55. Don't
know what 55 is, 12 means the PCM (or was it PMC) was disconnected from the
battery. I am going to get the reader again to reset the error.

Thanks

Jo


"Stephen Cowell" > wrote in message
. ..

"reigelser" > wrote in message
. ..
> To start the car I have to crank it once for a short time. Even If I crank
> longer it won't start. Then I turn the ignition off completely and start
> again and runs immediately.


You may have more than one problem... try this
sometime... turn on the key, let the thing sit for
ten seconds, then crank... should go vroom.
It this is what you're seeing, you have a fuel
pressure retention problem... either the back-
check valve, or a leaky injector.

> There was no service done prior to the Check
> engine light coming on. The wiper voltage seems very smooth and stable. I
> haven't measured the supply voltage while having the engine running yet.
> Everything else seems to run good: idle speed, kick down response. So
> would
> you recommend an engine cleaning first (engine compartment wasn't cleaned
> in
> a loooong time) and then a rework of the connectors?
> Thanks for all of your advice.


I'm not that big of a believer in engine cleaning...
especially when trying to troubleshoot a problem.
Don't compound your problems right now.. sounds
to me like you've got more than one.

Is the big braided ground wire still connected
between the block and firewall? Look good?

Get some Caig ProGold contact cleaner (sold at Fry's)
and put some in the connector (both ends) for the
TPS... try again. I want to verify that you've cleared
the old ECU code, and it keeps popping a new one...
am I right? Does it pop immediately, or after normal
in-town driving, or only after exhibiting the symptoms
you describe at 60-70mph transition?
__
Steve
..


Lastly, you may have to go through several run/drive
cycles for the ECU to learn the curve of the new TPS...


  #18  
Old June 15th 05, 03:23 AM
DougW
external usenet poster
 
Posts: n/a
Default

reigelser did pass the time by typing:
> I just tried the proposed starting procedure. KeyOnEngineoff for 10sec and
> then crank but no vroom. I needed a second try. When I turn the key I hear
> the Fuel pump for approx 1sec (I believe its the fuel pump).


Your correct, the pump runs (primes) the system for about 1 sec.

> With the engine
> cold there is a little delay in the throttle response. Between Pushing the
> throttle a bit and the revs coming up is a ~0.5sec delay. When I rev the
> engine at 2000 and go of the Throttle it goes all the way down to ~300rpm
> before it comes up to 800 again.0


That's normal. Your letting off the throttle is telling the engine to
go into braking mode.

> I checked the connectors (cleaned them with WD40)


WD-40 isn't a contact cleaner. Go to a local NAPA and get some
electrical contact cleaner that is safe for plastic. They make
two types, one is for cleaning alternators and you don't want that
one.

> and the ground cable:
> seem fine. Between engine block intake manifold and fire wall I measure ~0
> Ohm resistance, so the ground seems good.


That's good.

> I can not reset the error right know, because I don't have the reader
> available. But in the past I tried 50 times to reset the error and it is not
> erasable. Sometimes the light goes off, but comes back on immediately.
> Sometimes the device tells me, the error can't be erased.
> At the moment the Check ENgine Light readt out tells me 12, 24, 55. Don't
> know what 55 is, 12 means the PCM (or was it PMC) was disconnected from the
> battery. I am going to get the reader again to reset the error.


Recapping just a bit.

55 = end of codes
12 = battery disconnected within the last 50 power on/off cycles
and is only applicable if found with boatloads of other codes.
When you find it paired with lots of codes it is usually a bad
or loose battery cable. But it can indicate a faulty ground or
power wire to the PCM.
24 = Throttle position sensor input above or below acceptable
voltage. TPS signal does not correlate to MAP sensor.

With the ignition on, engine not running, backprobe the TPS.
One of the outer pins will have 5V on it. The other will have
zero. With the ignition OFF you should be able to probe between
the ground and the corresponding sensor grounds for the MAP, CPS, O2 sensor,
ECT and MAT sensors. Again, it helps to have the schematic with
your wire color codes. My 93 has black with light blue stripe as the
sensor grounds.

With the ignition ON, engine not running, measure the center pin.
Throttle closed > 200 milliVolts
Throttle wide open < 4.8 Volts
Anything in that range will adjust. The way you
adjust the TPS is by turning the key ON (engine not running)
then slowly cycle the throttle between full closed and full open
about 5-6 times. Then turn the ignition off.

See that second bit "TPS signal does not correlate to MAP sensor".
It could be the rubber hose between the MAP sensor and your inake has
a leak or the MAP sensor is failing. They can fail without setting
codes. They are of course bloody expensive and hard to test.

Just like the TPS sensor, the map sensor has three pins
A,B,C

A = Ground
B = output (.5v with ignition on, engine off)
C = 5V

There is no easy way of testing this doodad.


--
-- DougW -- 93 ZJ 4.0 http://members.cox.net/wilsond
HESCO Supercharger - 300W IASCA Stereo - Edelbrock IAS Shocks
Gibson Exhaust - rear DCpower - custom gauge install - Stillen Rotors
Banks Header - and BEER, in the fridge!


  #19  
Old June 15th 05, 05:06 AM
Stephen Cowell
external usenet poster
 
Posts: n/a
Default


"DougW" > wrote in message =
news:niMre.15993$mC.9041@okepread07...
> reigelser did pass the time by typing:
> > I just tried the proposed starting procedure. KeyOnEngineoff for =

10sec and
> > then crank but no vroom. I needed a second try. When I turn the key =

I hear
> > the Fuel pump for approx 1sec (I believe its the fuel pump).

>=20
> Your correct, the pump runs (primes) the system for about 1 sec.
>=20
> > With the engine
> > cold there is a little delay in the throttle response. Between =

Pushing the
> > throttle a bit and the revs coming up is a ~0.5sec delay. When I rev =

the
> > engine at 2000 and go of the Throttle it goes all the way down to =

~300rpm
> > before it comes up to 800 again.0

>=20
> That's normal. Your letting off the throttle is telling the engine to
> go into braking mode.


I disagree... 300rpm is not normal... I feel that the idle air
solenoid is closing down when he opens the throttle, then
motoring back up after the throttle hits the closed stop.
This certainly points to a TPS problem.... let's see what
happens after he performs the TPS alignment procedure
you gave.
__
Steve
..


  #20  
Old June 15th 05, 06:50 AM
Will Honea
external usenet poster
 
Posts: n/a
Default

On Wed, 15 Jun 2005 02:23:17 UTC "DougW"
> wrote:

> See that second bit "TPS signal does not correlate to MAP sensor".
> It could be the rubber hose between the MAP sensor and your inake has
> a leak or the MAP sensor is failing. They can fail without setting
> codes. They are of course bloody expensive and hard to test.


Just a slight expansion on your sequence her, Doug.

I've seen three cases where this problem was actually a dirty throttle
body. In one, the map port was clogged solid - took a small dril bit
and lots of cleaner followed by a pipe cleaner to get it working.

The other case was a buildup involving the idle air mixture. On the
one hand, there was enough buildup around the port to actually keep
the pintle on the IAC from seating while the buildup was sufficient to
actually grab the pintle and keep it from opening smoothly going the
other way. Cure was to remove the IAC motor and clean that idle air
port REALLY well.

The third case was on my 88 but I'm not sure the later MOPAR throttle
bodies have this and it sounds like yours is the later model. Mine
has an idle air bypass with the inlet on the top of the throttle body
and a needle valve near the base of the throttle body covered by a
tamper proof cover. I had to use an ice pick to remove that cover,
take the needle valve all the way out, and clean that entire channel
out - it was plugged solid. If you remove the needle valve, first
screw it all the way in (counting the turns) so that you can reset it
to where it was.

Long and the short of it: clean the throttle body REALLY well before
you throw too many parts at it. I finally pulled the throttle body
completely off and let it sit in cleaner in an ultrasonic cleaner for
an hour or so to get mine straightened out.

--
Will Honea
 




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