Long time reader, first time poster.  At my witts end.  Bear with me while I bring you up to speed. I have a 1998.5 2500 automatic 2wd with roughly 155K miles.  It was my grandfather's truck that I ended up with after his passing.  It wasn't in good running condition, but after some TLC it was a dream.  Work done includes - new turbo, ball joints, batteries, a/c, trailer wiring, tires, control arms, axle seals, belt, new suspension, cab lights, neutral safety switch, abs speed sensor, output speed sensor, and APPS.

Two years ago it went down on me one night while driving down the interstate, and I'm still trying to fix it.  I was on cruise and suddenly lost power, not died but lost 95% of it's output. The truck still cranks and runs fine but will only idle or jump to 1400-1500 rpm. There is no in-between or past. In gear it will barely roll in my flat driveway.  The truck has been with 3 mechanics without success and now it's back to me. 

I found continuity between my positive and negative battery cables. I tracked to C1 of the PCM and verified I had continuity to ground from pins 4 and 22.  I was also lacking ground continuity on C3 pin 28. I sent both the PCM and ECM to auto computer specialists and received them back this week.  I reinstalled and all of those continuity issues have been resolved.  

After installing the ECM and PCM my multimeter was still hooked up to my positive and negative battery terminals.  I opened the drivers door and heard the continuity tone.  I have since determined I have short to ground when either door is open or if the ignition is in run or the back position.  I have yet to understand the relation of the door jam switches and the ignition switch.  Confirmed it goes through the IOD fuse.  Attempting to track the short I came to this connector near the steering column.  I have been using the 1999 wiring diagrams for a while, but I am not able to find this connector with correct pin numbers. The pins circled have continuity to ground, but I'm not clear on their path from here. 

Apologies for such a long post. Any guidance on where to go from here is appreciated.

Before I can offer any help, I have some questions first.

1 hour ago, CH123 said:

After installing the ECM and PCM my multimeter was still hooked up to my positive and negative battery terminals.  I opened the drivers door and heard the continuity tone.  I have since determined I have short to ground when either door is open or if the ignition is in run or the back position.

Was your meter on the continuity (ohms) setting? Were the batteries connected or disconnected?

If the meter was set for continuity (ohms) and the batteries were disconnected, then it would be normal to have continuity between the positive cable and the ground cable when the door switch was activated. The current would be passing through the dome light and through the switch.

If the above paragraph doesn't represent what you observed, pleas let me know.

Can you provide more detail as to why you think you have a ground problem

• John

Edited Sunday at 01:57 AM4 days by Tractorman

1 hour ago, Tractorman said:

Before I can offer any help, I have some questions first.

Was your meter on the continuity (ohms) setting? Were the batteries connected or disconnected?

If the meter was set for continuity (ohms) and the batteries were disconnected, then it would be normal to have continuity between the positive cable and the ground cable when the door switch was activated. The current would be passing through the dome light and through the switch.

If the above paragraph doesn't represent what you observed, pleas let me know.

Can you provide more detail as to why you think you have a ground problem

• John

Setting shown in picture below.

I am tracking now with the batteries disconnected, however I also got the continuity tone with the batteries connected. I suspected the same regarding the dome light, but didn't understand why I have continuity with the ignition on, doors closed.

I am proceeding cautiously to ensure nothing is missed that may re-damage my PCM and ECM.

Your meter is set to "diode check" which means that current will flow only one way after it overcomes .6 volt. Current will not flow in the other direction.

1 hour ago, CH123 said:

I suspected the same regarding the dome light, but didn't understand why I have continuity with the ignition on, doors closed.

The continuity will be there with the ignition switch turned on for the same reason the continuity was there when the door was open. All it takes is one circuit to be activated with the ignition switch on to make continuity - for example, instrument panel indicator lamps. This would be normal.

Am I missing something here?

Why do you think you have a short to ground problem?

• John

Edited Sunday at 03:18 PM4 days by Tractorman

18 hours ago, Tractorman said:

Your meter is set to "diode check" which means that current will flow only one way after it overcomes .6 volt. Current will not flow in the other direction.

The continuity will be there with the ignition switch turned on for the same reason the continuity was there when the door was open. All it takes is one circuit to be activated with the ignition switch on to make continuity - for example, instrument panel indicator lamps. This would be normal.

Am I missing something here?

Why do you think you have a short to ground problem?

• John

So I shouldn't be worried about any of the wires circled in the first picture having "tone" to ground? What about when the engine is running?

If I should move on, I still have this throttle / power issue to resolve. Any guidance on where to focus or what sensors and target readings I should be seeing?

3 hours ago, CH123 said:

So I shouldn't be worried about any of the wires circled in the first picture having "tone" to ground? What about when the engine is running?

I can't answer that question as I don't know the purpose of that connector, or what you were trying to figure out with the method of testing you performed. If you don't know what is on either end of the connector, then any values from electrical tests performed are meaningless.

Please answer this question - why do you think you have a short to ground in the wiring on your truck? What is drawing you to this conclusion? You may have a valid reason - I am just not getting it.

Also, why are you using the "diode check" function on your meter to check for ground continuity (or shorts to ground) instead of using the resistance / ohms function?

If you can clear some of this up, then we can move on to trying to figure out the "no power" situation.

• John

14 hours ago, Tractorman said:

I can't answer that question as I don't know the purpose of that connector, or what you were trying to figure out with the method of testing you performed. If you don't know what is on either end of the connector, then any values from electrical tests performed are meaningless.

Please answer this question - why do you think you have a short to ground in the wiring on your truck? What is drawing you to this conclusion? You may have a valid reason - I am just not getting it.

Also, why are you using the "diode check" function on your meter to check for ground continuity (or shorts to ground) instead of using the resistance / ohms function?

If you can clear some of this up, then we can move on to trying to figure out the "no power" situation.

• John

That connector is a capped joint connector combining each cluster of colored wires into a single circuit. I believe it to be J/C 8 in the '99 wiring diagrams, but the pin numbers do not match this 1998.5.

I was under the impression I had an issue because I was getting the continuity tone sound on my battery cables even with the batteries in and engine running. This doesn't occur with my other vehicles in my driveway under the same conditions.

I just thought I was using the correct setting for this, but I can certainly switch to ohms for any readings you would like me to provide. Thank you for the help!

I appreciate your explanation.

The "diode check" function is used for checking alternator diodes. The meter itself applies a specific voltage value to the diode being tested in the free-flow direction. The meter displays that value in voltage - example: .650 volts for a good diode. Reverse the polarity and the meter would read OL (out of voltage limit). Also, it is worth noting that at least one end of the diode is removed from the circuit during the test, otherwise an erroneous reading or damage to the meter (if external power is supplied) may result.

Since you were using your meter's diode test function under various uncontrolled conditions (batteries disconnected, batteries connected, engine running, etc.), you were likely collecting many erroneous readings and also you risked damaging your multimeter.

The "resistance" test (Ohms) is used for checking continuity in wiring. The meter applies a specific voltage (similar to the "diode check") and measures the resistance of the circuit being tested. The meter displays the resulting value in Ohms. As in diode testing (and for the same reasons), the wire being tested must have at least one end removed from the circuit being tested and have NO external power applied.

Don't rely on the meter's "tone sound" for testing results. Look at the display and note the actual ohm reading. There are three tests that can be performed.

• One test will check the continuity of wire (should be almost zero ohms).

• Another test will check for continuity of the wire to a good ground source - a short circuit - (should be OL).

• The last test will check for continuity of the wire to any adjacent wire of your choice - a short circuit - (should be OL).

Prior to performing any continuity testing, always do the following:

• Set the meter to the lowest ohms scale - do not use the Kilo-ohms or Mega-ohms scale. Do not use auto scaling.

• Touch and hold your test leads together to prove that the meter and your test leads are performing properly. A reading of zero or near zero ohms is expected.

So, hopefully you will re-think how you do your future continuity testing. If you still believe that you have a short-to-ground issue, then be deliberate and test circuits that are relevant to prove whether or not the particular circuit is functioning properly. I'll be happy to help you through that.

• John

1 hour ago, Tractorman said:

I appreciate your explanation.

The "diode check" function is used for checking alternator diodes. The meter itself applies a specific voltage value to the diode being tested in the free-flow direction. The meter displays that value in voltage - example: .650 volts for a good diode. Reverse the polarity and the meter would read OL (out of voltage limit). Also, it is worth noting that at least one end of the diode is removed from the circuit during the test, otherwise an erroneous reading or damage to the meter (if external power is supplied) may result.

Since you were using your meter's diode test function under various uncontrolled conditions (batteries disconnected, batteries connected, engine running, etc.), you were likely collecting many erroneous readings and also you risked damaging your multimeter.

The "resistance" test (Ohms) is used for checking continuity in wiring. The meter applies a specific voltage (similar to the "diode check") and measures the resistance of the circuit being tested. The meter displays the resulting value in Ohms. As in diode testing (and for the same reasons), the wire being tested must have at least one end removed from the circuit being tested and have NO external power applied.

Don't rely on the meter's "tone sound" for testing results. Look at the display and note the actual ohm reading. There are three tests that can be performed.

• One test will check the continuity of wire (should be almost zero ohms).

• Another test will check for continuity of the wire to a good ground source - a short circuit - (should be OL).

• The last test will check for continuity of the wire to any adjacent wire of your choice - a short circuit - (should be OL).

Prior to performing any continuity testing, always do the following:

• Set the meter to the lowest ohms scale - do not use the Kilo-ohms or Mega-ohms scale. Do not use auto scaling.

• Touch and hold your test leads together to prove that the meter and your test leads are performing properly. A reading of zero or near zero ohms is expected.

So, hopefully you will re-think how you do your future continuity testing. If you still believe that you have a short-to-ground issue, then be deliberate and test circuits that are relevant to prove whether or not the particular circuit is functioning properly. I'll be happy to help you through that.

• John

Very helpful. So to provide more accurate information to the original post, here are ohms readings to ground from the wires at what I believe to be J/C 8 as well as the positive battery lead. If not listed, the reading was OL. I noted baseline readings and which ones didn't change through the variable conditions.

Baseline - door closed, ignition off.

positive battery terminal - 154

Green w/ yellow - 48.6, no changes

Black w/ pink - 0, no chnges

Back w/ pink -0, no changes

White w/ green - 8.1, no changes

Door open, ignition off-

Tan - 0

Yellow -0

Yellow - 6.1

White w/ green - 4.9

Positive battery terminal - 4.9

Door closed, ignition on-

Positive battery terminal - 40.1

Green w/ yellow - 48.6

Yellow 54.8

Yellow - 58.1

Black w/pink - 0

Let me know if any of these are concerning. If not, we can move on to the main issue of throttle and power.

I am kind of at a standstill here as I don't know what you are trying to accomplish with your tests on Joint Connector #8. Plus, it appears that you are testing for resistance (ohms), but you are breaking all of the rules mentioned in my previous post, such as leaving everything connected and supplying external power).

On 10/25/2025 at 5:17 PM, CH123 said:

After installing the ECM and PCM my multimeter was still hooked up to my positive and negative battery terminals.  I opened the drivers door and heard the continuity tone.  I have since determined I have short to ground when either door is open or if the ignition is in run or the back position.  I have yet to understand the relation of the door jam switches and the ignition switch.

This is from your original post. A previous post by me explained why this would be normal to have continuity through both the door switch and through the ignition switch under these conditions.

On 10/25/2025 at 5:17 PM, CH123 said:

Attempting to track the short I came to this connector near the steering column.  I have been using the 1999 wiring diagrams for a while, but I am not able to find this connector with correct pin numbers. The pins circled have continuity to ground, but I'm not clear on their path from here. 

This is the next part of the same paragraph from your original post. I am thinking there is no faulty short to track down. So, my question is - why are you focused on these particular wires? And, what are you testing for?

Hopefully, we can get this part resolved and move on to the real issue - lack of engine power.

• John

Edited Tuesday at 02:05 AM2 days by Tractorman

17 minutes ago, Tractorman said:

I am kind of at a standstill here as I don't know what you are trying to accomplish with your tests on Joint Connector #8. Plus, it appears that you are testing for resistance (ohms), but you are breaking all of the rules mentioned in my previous post, such as leaving everything connected and supplying external power).

This is from your original post. A previous post by me explained why this would be normal to have continuity through both the door switch and through the ignition switch under these conditions.

This is the next part of the same paragraph from your original post. I am thinking there is no faulty short to track down. So, my question is - why are you focused on these particular wires? And, what are you testing for?

Hopefully, we can get this part resolved and move on to the real issue - lack of engine power.

• John

I did not have any external power sources such as batteries connected. I am no longer focused on these wires. Ready to move on.

Glad to hear that you didn't have the battery connected during the tests.

On 10/25/2025 at 5:17 PM, CH123 said:

I was on cruise and suddenly lost power, not died but lost 95% of it's output. The truck still cranks and runs fine but will only idle or jump to 1400-1500 rpm. There is no in-between or past. In gear it will barely roll in my flat driveway.  The truck has been with 3 mechanics without success and now it's back to me. 

I am referring back to your original post as a starting point. Has anyone checked for codes? If so, what are they? If codes have been checked and there are no codes, there are other things to be checked off the list, such as:

• Did you fuel the truck just before this incident occurred? (possible water contamination or wrong fuel)

• Have you verified lift pump pressure?

• Is the lift pump running? The lift pump should run for 1/4 second with key in Run position. Switch key to Off position and then to Bump Starter position (don't start the engine) and let the key return to Run position. You should hear the lift pump run for about 20 seconds. Be sure to always turn the key to the Off position before repeating a test.

Check over the positive and negative battery cables and connections carefully. Don't forget the crossover cable. Use your 99 wiring diagram to find and check grounds - especially for the ECM, PCM, PDC and the VP44.

This will be a good start. Let me know what you find.

• John

Edited Tuesday at 04:06 AM2 days by Tractorman

8 hours ago, Tractorman said:

Glad to hear that you didn't have the battery connected during the tests.

I am referring back to your original post as a starting point. Has anyone checked for codes? If so, what are they? If codes have been checked and there are no codes, there are other things to be checked off the list, such as:

• Did you fuel the truck just before this incident occurred? (possible water contamination or wrong fuel)

• Have you verified lift pump pressure?

• Is the lift pump running? The lift pump should run for 1/4 second with key in Run position. Switch key to Off position and then to Bump Starter position (don't start the engine) and let the key return to Run position. You should hear the lift pump run for about 20 seconds. Be sure to always turn the key to the Off position before repeating a test.

Check over the positive and negative battery cables and connections carefully. Don't forget the crossover cable. Use your 99 wiring diagram to find and check grounds - especially for the ECM, PCM, PDC and the VP44.

This will be a good start. Let me know what you find.

• John

I am out of town for a couple days, but here's what I can answer now-

At the time the truck went down I showed codes 1689, 1693, and 0720. Not 100% certain all were new since I had some sensors replaced about a month prior, and can't recall if any codes present had been cleared (2 years ago now). Once I received the truck back to my possession a couple months ago the OBD was no longer communicating. I have not yet checked since reinstalling the ECM and PCM this week. I will check Friday.

I had been on the road about an hour and half since my last refuel.

Lift pump is working. At my last check it was around 13 PSI.

I asked the last mechanic to inspect the battery connections. He did cut back some of the coating and confirmed there was not any corrosion inside. I'll reinspect all and the grounds once I'm back Friday.

Sounds like a good plan. Thanks for the informative response - good information.

• John