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Renix gurus needed!

Smash Hole

Smash Hole

GFY
Location
Smash HQ
88 Comanche 4.0/AW4/231

TPS, ECT, IAT, O2, MAP and fuel trims are maxed. I have run auxiliary grounds to the ALL the sensors to battery. I have grounded the ecu directly, and have bypassed the c101 connector.

Snapon MT2500 Jeep 1 connector

AT IDLE
Map: 4.98v
Map: 31" Hg
Short term fuel trim: 128
Long term fuel trim: 128
Exhaust: lean
Open Loop
O2: 4.98v
Inj. 18.3 ms
Rpm: 850
Spark: 4%
Coolant temp: 246*
Air temp: 246*
TPS: WOT
Throttle: 100%
Vacuum: 0
Baro: 31" Hg

Truck is full on rich, but still runs surprisingly well. New O2 and MAP. Both did absolutely nothing.

I'm out of ideas. I'm starting to think the ECU is fried but I've never heard of this situation. Any ideas
 
Last edited:
Vacuum: 0

are you positive the vacuum line to the MAP sensor isn't stopped up with crud? I can't see how you would have 0 inches if it's running. Try a different vacuum port and another hose/line just for fun.
 
Shorty said:
Vacuum: 0

are you positive the vacuum line to the MAP sensor isn't stopped up with crud? I can't see how you would have 0 inches if it's running. Try a different vacuum port and another hose/line just for fun.
Click to expand...

It's a new line and the sensor was vacuum tested. Plus all the other sensors are maxed out.
 
The vacuum connector from the map into the throttle body can be inserted upside down. Verify that the hose on the rubber insert is indeed lined up with the hole in the throttle body. I can't remember if it goes up or down.
 
old_man said:
The vacuum connector from the map into the throttle body can be inserted upside down. Verify that the hose on the rubber insert is indeed lined up with the hole in the throttle body. I can't remember if it goes up or down.
Click to expand...

It's all good. It's sucking on my finger as I type.
 
check the ohm readings on both the coolant temp switch on the side of the block and the air temp sensor on the back side of the intake. If either are bad it can cause those to read default max on the MT2500. Both sensors use the same degree F to ohm reading chart. If you have a Chilton book its on section 4-23 and 4-24. I just did mine after seeing the readings on my MT2500 and low and behold my coolant temp sensor was good but my air temp sensor was waaaaayyyy outta spec.. You have to test both the sensors unplugged.

You can manually check most with a DVM(digital volt meter) Here is a link to a very helpful bit of info.....

http://www.lunghd.com/Tech_Articles/Engine/Basic_Sensors_Diagnostics.htm
 
Make sure that the grounds that are on the oil dipstick are clean and tight as well. Just those grounds right there can cause havoc.
 
Your O2 is showing Lean & the voltage is high this equals lean, the Throttle is 100%, Coolant 246*, Air Temp 246* and no Vacuum this is all wrong! I would start by checking the MAP line, then the TPS & CTS.I believe 246* is an open thermocouple. Check the grounds at the sensors.
 
Have you done anything major or not major for that matter to it.. Any thing at all may be worth a mention..
 
kcjeep6 said:
Your O2 is showing Lean & the voltage is high this equals lean, the Throttle is 100%, Coolant 246*, Air Temp 246* and no Vacuum this is all wrong! I would start by checking the MAP line, then the TPS & CTS.I believe 246* is an open thermocouple. Check the grounds at the sensors.
Click to expand...

EXACTLY! It's as if every sensor has lost its grounds

The Comanche was bought with 2 spit main bearing caps, a hacked wiring harness, and the ugliest tail lights ever. I'm sure a lot of you know which one I'm talking about. I put a new long block and axles under it. Finally got it running after about a year under the knife.

Getting this thing to start with the hacked harness was a feat in itself. It's very possible that some wires could be (or been) crossed though trial and error. I'm pretty sure that that issue has been solved considering how well it runs despite this severe issue.
 
Check and report the actual voltages at the sensors with an ohm meter. If you actually have 5 volts at the sensors from the ECU, then ECU is not completely dead. Sure sounds like there is NO GROUND at the sensors, but you say you grounded them all to the battery, did you verify the grounds from each sensor to the battery?

Are you sure the ECU sensor ground at the oil dipstick is good, all the way back to the battery?

The engine would not be running with a totally dead ECU!!!!

Is the scanner having a problem, is it grounded?
 
Last edited:
Don’t start thinking it's the ECU, the thing is still running that means your ECU is working, I’ve made that mistake! I feel you hit the nail on the head with that Grounds idea.
 
Done this?

Cruiser’s Renix Sensor Ground Test
　
This sensor ground circuit affects the CTS, TPS, IAT, MAP, ECU and diagnostic connector grounds. It’s very important and not something to overlook in diagnosing your Renix Jeep as it is common for the harnesses to have poor crimps causing poor grounds. If any or all of the sensors do not have a good ground, the signal the ECU receives from these sensors is inaccurate.
Set your meter to measure Ohms. Be sure the key is in the OFF position. Using the positive (red) lead of your ohmmeter, probe the B terminal of the flat 3 wire connector of the TPS . The letters are embossed on the connector itself.
Touch the black lead of your meter to the negative battery post. Wiggle the wiring harness where it runs parallel to the valve cover and also near the MAP sensor mounted on the firewall. If you have an 87 or 88 with the C101 connector mounted on the firewall above the brake booster, wiggle it, too.
You want to see as close to 0 ohms of resistance as possible. And when wiggling the harnesses/connectors the resistance value should stay low. If there is a variance in the values when wiggling the wires, you have a poor crimp/connection in the wiring harness or a poor ground at the engine dipstick tube stud. On 87 and 88 models, you could have a poor connection at the C101 connector as well.
Revised 06/12/2012
 
cruiser54 said:
Done this?

Cruiser’s Renix Sensor Ground Test
　
This sensor ground circuit affects the CTS, TPS, IAT, MAP, ECU and diagnostic connector grounds. It’s very important and not something to overlook in diagnosing your Renix Jeep as it is common for the harnesses to have poor crimps causing poor grounds. If any or all of the sensors do not have a good ground, the signal the ECU receives from these sensors is inaccurate.
Set your meter to measure Ohms. Be sure the key is in the OFF position. Using the positive (red) lead of your ohmmeter, probe the B terminal of the flat 3 wire connector of the TPS . The letters are embossed on the connector itself.
Touch the black lead of your meter to the negative battery post. Wiggle the wiring harness where it runs parallel to the valve cover and also near the MAP sensor mounted on the firewall. If you have an 87 or 88 with the C101 connector mounted on the firewall above the brake booster, wiggle it, too.
You want to see as close to 0 ohms of resistance as possible. And when wiggling the harnesses/connectors the resistance value should stay low. If there is a variance in the values when wiggling the wires, you have a poor crimp/connection in the wiring harness or a poor ground at the engine dipstick tube stud. On 87 and 88 models, you could have a poor connection at the C101 connector as well.
Revised 06/12/2012
Click to expand...

Each sensor has its own dedicated ground to the battery
 
Ecomike said:
Check and report the actual voltages at the sensors with an ohm meter. If you actually have 5 volts at the sensors from the ECU, then ECU is not completely dead. Sure sounds like there is NO GROUND at the sensors, but you say you grounded them all to the battery, did you verify the grounds from each sensor to the battery?

Are you sure the ECU sensor ground at the oil dipstick is good, all the way back to the battery?

The engine would not be running with a totally dead ECU!!!!

Is the scanner having a problem, is it grounded?
Click to expand...

I grounded the ECU directly at the pin to the battery. Each sensor was grounded directly to the battery with a bypass

Yesterday I was getting the 5v reference voltages at the o2 and at the TPS. I did not go any farther than that as I assumed I had a major ground issue and started bypassing everything directly to the battery.

The scanner not being grounded does intrigue me. I'm going to look at the diagnostic connector a little closer tomorrow.
 
Hey guys, you don't measure voltages with an Ohm meter. Ohms are a unit of resistance. You measure voltage with a Volt meter or a multi-meter. Hasta

To check your grounds, hook one side of the volt meter to the negative terminal on the battery and then probe the ground on the sensor with it running. It should read approximately ground. IIRC, something around .2 Volts is acceptable. It the voltage is below that, the ground is not the problem.

You do have the ground from the rear of the head to the firewall, correct?
 
old_man said:
Hey guys, you don't measure voltages with an Ohm meter. Ohms are a unit of resistance. You measure voltage with a Volt meter or a multi-meter. Hasta

To check your grounds, hook one side of the volt meter to the negative terminal on the battery and then probe the ground on the sensor with it running. It should read approximately ground. IIRC, something around .2 Volts is acceptable. It the voltage is below that, the ground is not the problem.

You do have the ground from the rear of the head to the firewall, correct?
Click to expand...

I do have the engine grounded and I have also have to jumper cable to battery during my testing.

I have been checking voltage drops.

The data I am getting is not making any sense. All of my testing indicates all the sensors are doing their jobs but somewhere in between the sensors; either the scanner is interpreting the data wrong, or the ECU thinks the sensors have lost their grounds. Every single sensor is pegged max on my scanner and unplugging the individual sensors does nothing to the driveability. I'm thinking because it is staying in open loop, the ecu is operating off of set values which explains why unplugging the sensors do nothing.

It would be one thing if it was just the TPS maxed, but EVERY one of my sensors are maxed (at the scanner)
 
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