1987 JEEP : TPS Question

1987 JEEP CHEROKEE CHIEF, 4Door,4WD, 6 cyl 4.0L Automatic
VIN# xJCMRxxxxHTxxxxxx with a RENIX ECU.

Where does the Throttle Position Sensor input voltage come from?

I replaced the TPS 2 years ago and calibrated the OUT divided by the IN
@ 83%, and it worked well until recently.

My current TPS readings are IN = 7.81 vdc, and OUT = 5.65 vdc.

I am suspecting my problems are centered in the origin of the voltage
being supplied too high to the TPS and not the TPS itself.

Any advice is welcomed, thanks.

Electronic Control Module: http://www.billhughes.com/temp/87jeepwire.pdf
You forgot to tell us what you think it's doing, or not.
God Bless America, Bill O|||||||O

http://www.billhughes.com/jeep_bookmark.htm

> wrote in message
m...
> 1987 JEEP CHEROKEE CHIEF, 4Door,4WD, 6 cyl 4.0L Automatic
> VIN# xJCMRxxxxHTxxxxxx with a RENIX ECU.
>
> Where does the Throttle Position Sensor input voltage come from?
>
> I replaced the TPS 2 years ago and calibrated the OUT divided by the IN
> @ 83%, and it worked well until recently.
>
> My current TPS readings are IN = 7.81 vdc, and OUT = 5.65 vdc.
>
> I am suspecting my problems are centered in the origin of the voltage
> being supplied too high to the TPS and not the TPS itself.
>
> Any advice is welcomed, thanks.

wrote:

> 1987 JEEP CHEROKEE CHIEF, 4Door,4WD, 6 cyl 4.0L Automatic
> VIN# xJCMRxxxxHTxxxxxx with a RENIX ECU.
>
> Where does the Throttle Position Sensor input voltage come from?
>
> I replaced the TPS 2 years ago and calibrated the OUT divided by the IN
> @ 83%, and it worked well until recently.
>
> My current TPS readings are IN = 7.81 vdc, and OUT = 5.65 vdc.
>
> I am suspecting my problems are centered in the origin of the voltage
> being supplied too high to the TPS and not the TPS itself.
>
> Any advice is welcomed, thanks.

The factory manual for the Renix system (same as my '88 Commanche) says that
the reference voltage should be 5.0 volts supplied by the computer but
yours may be running slightly differently. My adjustment procedure (from
the manual) is .86 volts ouput with the throttle at dead idle to 4.95 at
WOT. If it is the 5.0 reference, you'll also find that the MAP sensor
supply is high. If that's the case, good luck finding another computer!
As I recall, the Rennix system was only used in 87 and 88 - maybe a few of
early the 89's had it butthe 90's on used the MOPAR unit. That had totally
different sensors and was set up for the HO engine with different intake
manifolds and headers along with a reworked head. If the engine runs OK
beyond the idle/WOT performance, you might be able to repair the voltage
reference inside the computer but that's chancy - I've never gotten the
schematics for that beast.

--
Will Honea

The ECU supplies both voltage and ground to the sensors.

There are two splices in the sensor ground circuit that have been very
troublesome on the early (87 and early 88) 4.0L XJ/MJ. They used a
bulkhead connector on the firewall that connected the engine harness
to the injector harness. The splices are within about a foot of that
connector, one on each side. They are crimped and duct taped inside
the harness.

In the engine harness, there is a 3 into 1 splice. The single wire
goes through the bulkhead connector, then a 1 into 3 splice in the
injector harness. The circuit is brown with white tracer.

You can manipulate the harnesses in the area of the splices and watch
the TPS voltage go nuts with a scan tool. I've never seen a physical
problem with the splices (no broken wires, corrosion or high
resistance), so it appears to be the way they routed the wires in the
harness. Maybe too close to, or not protected well enough, from other
current carrying wires. Whatever it is, you can open the harnesses
and pull the splices out, isolating them from the harness and the
problem goes away.

Since the bulkhead connector can be problematic also, I'd suggest
bypassing it altogether. Just solder the 3 wires in the engine
harness to the 3 in the injector harness. The splices are close enough
to each other that it's easy to do. Tape it up and it looks good and
no more problems.



On Thu, 17 Sep 2009 15:30:35 -0600, wrote:

>1987 JEEP CHEROKEE CHIEF, 4Door,4WD, 6 cyl 4.0L Automatic
>VIN# xJCMRxxxxHTxxxxxx with a RENIX ECU.
>
>Where does the Throttle Position Sensor input voltage come from?
>
>I replaced the TPS 2 years ago and calibrated the OUT divided by the IN
>@ 83%, and it worked well until recently.
>
>My current TPS readings are IN = 7.81 vdc, and OUT = 5.65 vdc.
>
>I am suspecting my problems are centered in the origin of the voltage
>being supplied too high to the TPS and not the TPS itself.
>
>Any advice is welcomed, thanks.

Bill Hughes, Will, & Bllsht,

Thank each of you for responding.

When I posted the message, I decided to jump into the jeep and go
purchase a new TPS as a last ditch effort when I considered the other
possible costs.

My initial symptoms started ALL at once, back in May this year. While
driving on the interstate, the transmission when out (save 1st gear &
some second). Low fluid. So I immediately added enough fluid to get home.

The transmission wouldn't work properly and also started having engine
idle problems (cold start kills, and also at running temperature having
very high idles).

I dropped the pan, changed the screen, cleaned the magnet (slight haze
covering it, no shavings), and the bottom of the pan was absolutely free
of debris. The fluid smelled new and clear (zero burn scent). I put on a
new screen and replaced the fluid, adding some lucas as a kicker.

I brought it into several shops and they would only tell me "oh, about
two thousand dollars", but yet I'd hit a bump and I'd have 4 gears back
up shifting and down shifting normally as if I never had a problem (but
the idle problem prevailed).

Each time the transmission would randomly go ignorant, I'd checked the
TPS. Each time it reported in @ 83ish% --until September. Once I
replaced the TPS and calibrated, the idle issue when away -- and so did
the transmission issue (save one). I did not get overdrive back. It's
been a month, and I am at another dead end on what direction I should take.

I do not know if I damaged the 4th gear/overdrive planetary when I ran
low on fluid (temperature wise) back in May, or if I have a pending
overdrive electronic issue? MT2500 didn't shed any usable clues.

Based upon each of your previous postings with advise, I am going to
break open & look into the wiring harness and also disconnect at the
bulkhead to check the contacts this weekend.

Do you think my neutral safety switch is over due at 270k miles?
--Percentage wise? Aisin Warner 30-40LE.

Any Suggestions?
Thanks,
Ken



Will Honea wrote:
> wrote:
>
>> 1987 JEEP CHEROKEE CHIEF, 4Door,4WD, 6 cyl 4.0L Automatic
>> VIN# xJCMRxxxxHTxxxxxx with a RENIX ECU.
>>
>> Where does the Throttle Position Sensor input voltage come from?
>>
>> I replaced the TPS 2 years ago and calibrated the OUT divided by the IN
>> @ 83%, and it worked well until recently.
>>
>> My current TPS readings are IN = 7.81 vdc, and OUT = 5.65 vdc.
>>
>> I am suspecting my problems are centered in the origin of the voltage
>> being supplied too high to the TPS and not the TPS itself.
>>
>> Any advice is welcomed, thanks.
>
> The factory manual for the Renix system (same as my '88 Commanche) says that
> the reference voltage should be 5.0 volts supplied by the computer but
> yours may be running slightly differently. My adjustment procedure (from
> the manual) is .86 volts ouput with the throttle at dead idle to 4.95 at
> WOT. If it is the 5.0 reference, you'll also find that the MAP sensor
> supply is high. If that's the case, good luck finding another computer!
> As I recall, the Rennix system was only used in 87 and 88 - maybe a few of
> early the 89's had it butthe 90's on used the MOPAR unit. That had totally
> different sensors and was set up for the HO engine with different intake
> manifolds and headers along with a reworked head. If the engine runs OK
> beyond the idle/WOT performance, you might be able to repair the voltage
> reference inside the computer but that's chancy - I've never gotten the
> schematics for that beast.
>

wrote:

> Bill Hughes, Will, & Bllsht,
>
> Thank each of you for responding.
>
> When I posted the message, I decided to jump into the jeep and go
> purchase a new TPS as a last ditch effort when I considered the other
> possible costs.
>
> My initial symptoms started ALL at once, back in May this year. While
> driving on the interstate, the transmission when out (save 1st gear &
> some second). Low fluid. So I immediately added enough fluid to get home.
>
> The transmission wouldn't work properly and also started having engine
> idle problems (cold start kills, and also at running temperature having
> very high idles).
>
> I dropped the pan, changed the screen, cleaned the magnet (slight haze
> covering it, no shavings), and the bottom of the pan was absolutely free
> of debris. The fluid smelled new and clear (zero burn scent). I put on a
> new screen and replaced the fluid, adding some lucas as a kicker.
>
> I brought it into several shops and they would only tell me "oh, about
> two thousand dollars", but yet I'd hit a bump and I'd have 4 gears back
> up shifting and down shifting normally as if I never had a problem (but
> the idle problem prevailed).
>
> Each time the transmission would randomly go ignorant, I'd checked the
> TPS. Each time it reported in @ 83ish% --until September. Once I
> replaced the TPS and calibrated, the idle issue when away -- and so did
> the transmission issue (save one). I did not get overdrive back. It's
> been a month, and I am at another dead end on what direction I should
> take.
>
> I do not know if I damaged the 4th gear/overdrive planetary when I ran
> low on fluid (temperature wise) back in May, or if I have a pending
> overdrive electronic issue? MT2500 didn't shed any usable clues.
>
> Based upon each of your previous postings with advise, I am going to
> break open & look into the wiring harness and also disconnect at the
> bulkhead to check the contacts this weekend.
>
> Do you think my neutral safety switch is over due at 270k miles?
> --Percentage wise? Aisin Warner 30-40LE.
>
> Any Suggestions?
> Thanks,
> Ken
>
>
>
> Will Honea wrote:
>> wrote:
>>
>>> 1987 JEEP CHEROKEE CHIEF, 4Door,4WD, 6 cyl 4.0L Automatic
>>> VIN# xJCMRxxxxHTxxxxxx with a RENIX ECU.
>>>
>>> Where does the Throttle Position Sensor input voltage come from?
>>>
>>> I replaced the TPS 2 years ago and calibrated the OUT divided by the IN
>>> @ 83%, and it worked well until recently.
>>>
>>> My current TPS readings are IN = 7.81 vdc, and OUT = 5.65 vdc.
>>>
>>> I am suspecting my problems are centered in the origin of the voltage
>>> being supplied too high to the TPS and not the TPS itself.
>>>
>>> Any advice is welcomed, thanks.
>>
>> The factory manual for the Renix system (same as my '88 Commanche) says
>> that the reference voltage should be 5.0 volts supplied by the computer
>> but
>> yours may be running slightly differently. My adjustment procedure (from
>> the manual) is .86 volts ouput with the throttle at dead idle to 4.95 at
>> WOT. If it is the 5.0 reference, you'll also find that the MAP sensor
>> supply is high. If that's the case, good luck finding another computer!
>> As I recall, the Rennix system was only used in 87 and 88 - maybe a few
>> of
>> early the 89's had it butthe 90's on used the MOPAR unit. That had
>> totally different sensors and was set up for the HO engine with different
>> intake
>> manifolds and headers along with a reworked head. If the engine runs OK
>> beyond the idle/WOT performance, you might be able to repair the voltage
>> reference inside the computer but that's chancy - I've never gotten the
>> schematics for that beast.
>>

At 276k on the clock, the whole power train is tired and the tranny has all
sorts of worn parts, so I pass on that. For the idle, just unplug the TPS
(both of them) and clean the plug contacts with contact cleaner.

--
Will Honea

On Tue, 27 Oct 2009 09:39:55 -0600, wrote:

>Bill Hughes, Will, & Bllsht,
>
>Thank each of you for responding.
>
>When I posted the message, I decided to jump into the jeep and go
>purchase a new TPS as a last ditch effort when I considered the other
>possible costs.
>
>My initial symptoms started ALL at once, back in May this year. While
>driving on the interstate, the transmission when out (save 1st gear &
>some second). Low fluid. So I immediately added enough fluid to get home.
>
>The transmission wouldn't work properly and also started having engine
>idle problems (cold start kills, and also at running temperature having
>very high idles).
>
>I dropped the pan, changed the screen, cleaned the magnet (slight haze
>covering it, no shavings), and the bottom of the pan was absolutely free
>of debris. The fluid smelled new and clear (zero burn scent). I put on a
>new screen and replaced the fluid, adding some lucas as a kicker.
>
>I brought it into several shops and they would only tell me "oh, about
>two thousand dollars", but yet I'd hit a bump and I'd have 4 gears back
>up shifting and down shifting normally as if I never had a problem (but
>the idle problem prevailed).
>
>Each time the transmission would randomly go ignorant, I'd checked the
>TPS. Each time it reported in @ 83ish% --until September. Once I
>replaced the TPS and calibrated, the idle issue when away -- and so did
>the transmission issue (save one). I did not get overdrive back. It's
>been a month, and I am at another dead end on what direction I should take.
>
>I do not know if I damaged the 4th gear/overdrive planetary when I ran
>low on fluid (temperature wise) back in May, or if I have a pending
>overdrive electronic issue? MT2500 didn't shed any usable clues.
>
>Based upon each of your previous postings with advise, I am going to
>break open & look into the wiring harness and also disconnect at the
>bulkhead to check the contacts this weekend.
>
>Do you think my neutral safety switch is over due at 270k miles?
>--Percentage wise? Aisin Warner 30-40LE.

When you put a scan tool on it, what DTCs do you get?

"PeterD" > wrote in message
...
> On Tue, 27 Oct 2009 09:39:55 -0600, wrote:
>
>>Bill Hughes, Will, & Bllsht,
>>
>>Thank each of you for responding.
>>
>>When I posted the message, I decided to jump into the jeep and go
>>purchase a new TPS as a last ditch effort when I considered the other
>>possible costs.
>>
>>My initial symptoms started ALL at once, back in May this year. While
>>driving on the interstate, the transmission when out (save 1st gear &
>>some second). Low fluid. So I immediately added enough fluid to get home.
>>
>>The transmission wouldn't work properly and also started having engine
>>idle problems (cold start kills, and also at running temperature having
>>very high idles).
>>
>>I dropped the pan, changed the screen, cleaned the magnet (slight haze
>>covering it, no shavings), and the bottom of the pan was absolutely free
>>of debris. The fluid smelled new and clear (zero burn scent). I put on a
>>new screen and replaced the fluid, adding some lucas as a kicker.
>>
>>I brought it into several shops and they would only tell me "oh, about
>>two thousand dollars", but yet I'd hit a bump and I'd have 4 gears back
>>up shifting and down shifting normally as if I never had a problem (but
>>the idle problem prevailed).
>>
>>Each time the transmission would randomly go ignorant, I'd checked the
>>TPS. Each time it reported in @ 83ish% --until September. Once I
>>replaced the TPS and calibrated, the idle issue when away -- and so did
>>the transmission issue (save one). I did not get overdrive back. It's
>>been a month, and I am at another dead end on what direction I should
>>take.
>>
>>I do not know if I damaged the 4th gear/overdrive planetary when I ran
>>low on fluid (temperature wise) back in May, or if I have a pending
>>overdrive electronic issue? MT2500 didn't shed any usable clues.
>>
>>Based upon each of your previous postings with advise, I am going to
>>break open & look into the wiring harness and also disconnect at the
>>bulkhead to check the contacts this weekend.
>>
>>Do you think my neutral safety switch is over due at 270k miles?
>>--Percentage wise? Aisin Warner 30-40LE.
>
> When you put a scan tool on it, what DTCs do you get?


It's an '87, not '97. There is no scan tool to pull DTCs.

PeterD,
I do not own a mt2500, but I found someone who had one. We were not able
to get any specific codes from the ecu or the tcu, but all of the basic
reporting features illustrated nominal/pass results. I heard it said
that a DRB II would do nicely but no shop in the city has one. I have
the Renix ECU made by Bendix (replaced with a new one 2 years ago).

What do you think?
Ken

PeterD wrote:
> On Tue, 27 Oct 2009 09:39:55 -0600, wrote:
>
>> Bill Hughes, Will, & Bllsht,
>>
>> Thank each of you for responding.
>>
>> When I posted the message, I decided to jump into the jeep and go
>> purchase a new TPS as a last ditch effort when I considered the other
>> possible costs.
>>
>> My initial symptoms started ALL at once, back in May this year. While
>> driving on the interstate, the transmission when out (save 1st gear &
>> some second). Low fluid. So I immediately added enough fluid to get home.
>>
>> The transmission wouldn't work properly and also started having engine
>> idle problems (cold start kills, and also at running temperature having
>> very high idles).
>>
>> I dropped the pan, changed the screen, cleaned the magnet (slight haze
>> covering it, no shavings), and the bottom of the pan was absolutely free
>> of debris. The fluid smelled new and clear (zero burn scent). I put on a
>> new screen and replaced the fluid, adding some lucas as a kicker.
>>
>> I brought it into several shops and they would only tell me "oh, about
>> two thousand dollars", but yet I'd hit a bump and I'd have 4 gears back
>> up shifting and down shifting normally as if I never had a problem (but
>> the idle problem prevailed).
>>
>> Each time the transmission would randomly go ignorant, I'd checked the
>> TPS. Each time it reported in @ 83ish% --until September. Once I
>> replaced the TPS and calibrated, the idle issue when away -- and so did
>> the transmission issue (save one). I did not get overdrive back. It's
>> been a month, and I am at another dead end on what direction I should take.
>>
>> I do not know if I damaged the 4th gear/overdrive planetary when I ran
>> low on fluid (temperature wise) back in May, or if I have a pending
>> overdrive electronic issue? MT2500 didn't shed any usable clues.
>>
>> Based upon each of your previous postings with advise, I am going to
>> break open & look into the wiring harness and also disconnect at the
>> bulkhead to check the contacts this weekend.
>>
>> Do you think my neutral safety switch is over due at 270k miles?
>> --Percentage wise? Aisin Warner 30-40LE.
>
> When you put a scan tool on it, what DTCs do you get?

On Thu, 29 Oct 2009 11:37:16 -0600, wrote:

>PeterD,
>I do not own a mt2500, but I found someone who had one. We were not able
>to get any specific codes from the ecu or the tcu, but all of the basic
>reporting features illustrated nominal/pass results. I heard it said
>that a DRB II would do nicely but no shop in the city has one. I have
>the Renix ECU made by Bendix (replaced with a new one 2 years ago).
>
>What do you think?
>Ken
>

Some ECU/TCUs will inhibit overdrive if there are codes, but that
doesn't seem to be the problem. I'm not sure what's up at this stage.