LM7/Manual Drive By Cable P0507 code: SOLVED (1 Viewer)

[h82crash]

Any PCM gurus out there? No vacuum leaks, 650 smooth idle, no VSS, no stalling on decel. Relentless P0507 "Idle speed higher than expected."

Will the absence of a VSS to the PCM cause the P0507 code? Seems to me it's plausible. PCM assumes idle speed off throttle but drive train pulls RPMs up on decel.

Anyone else have to solve this issue?

EDIT: P0507 most likely due to no VSS to the PCM. P0135 was an exhaust leak. It shouldn't have taken me this long to fix it. I guess we never stop learning.

 

[peesalot]

I did a howell harness & comp, no VSS, 2 O2's, it runs rich when coming to a stop and rumbles for a sec but never dies just takes a bit for the comp to catch up the fuel curve based on the engine speed from crank sensor vs the VSS which is a much faster reading. What comp youusing, has anyone played with the tune ? Is your crank sensor in the comp set for the right tooth count on the tone ring ?

 

[peesalot]

IIRC its a crank position sensor or something, not a VSS that brings the idle down & adjusts fuel when there is no VSS, sounds like your tune deleted the VSS but did not pick up the signal from another sensor. It uses the engine rpm vs vehicle speed. Do you have the software so you can see whats going on ?

 

[cruisermatt]

Any PCM gurus out there? No vacuum leaks, 650 smooth idle, no VSS, no stalling on decel. Relentless P0507 "Idle speed higher than expected."

Will the absence of a VSS to the PCM cause the P0507 code? Seems to me it's plausible. PCM assumes idle speed off throttle but drive train pulls RPMs up on decel.

Anyone else have to solve this issue?

P0507 is actually often CTS. Try unplugging it it, clear the code and see if the p0507 goes away. It will throw a CTS code. Try the same thing with the IAC.

If it is running and driving well without the VSS then it's not the VSS. It's very 50/50 hit or miss whether you need one or not with manual/th350/400, and has never thrown a code from my experience.

Worst case you have someone tune it (you can probably pick up 10-15hp) and delete the code with HP Tuners if you don't figure it out.

 

[cruisermatt]

I did a howell harness & comp, no VSS, 2 O2's, it runs rich when coming to a stop and rumbles for a sec but never dies just takes a bit for the comp to catch up the fuel curve based on the engine speed from crank sensor vs the VSS which is a much faster reading. What comp youusing, has anyone played with the tune ? Is your crank sensor in the comp set for the right tooth count on the tone ring ?

I bet if you added a VSS it would clean that up. It can be mounted on the T-case and read the rear driveshaft studs, or on the knuckle and ready the wheel studs, or Tap your PTO cover and rear the T-case input gear, VSS tooth count doesn't matter for manual/non-electric auto

And there is absolutely no way the engine would run if the PCM and crank tone ring weren't matched.

 

[cruisermatt]

IIRC its a crank position sensor or something, not a VSS that brings the idle down & adjusts fuel when there is no VSS, sounds like your tune deleted the VSS but did not pick up the signal from another sensor. It uses the engine rpm vs vehicle speed. Do you have the software so you can see whats going on ?

This is not correct, DBC Gen 3 uses crank, cam, CTS, MAP, MAF, TPS, VSS altogether in harmony to open/close the IAC valve, not fuel, to adjust idle speed. It's not a diesel.

 

[peesalot]

OK, you are correct, I didnt feel the need to explain how the engine meters the fuel/air and my post could have been more elaborate.
Mine is not a daily and it isnt to bad at all, mainly the smell that drifts by as you stop cause no top. I have found that it is helpful when in low , low, it will dam near stall and keep running it amazes me and has never let me down so I ain changin nothin. I do agree that a vss would be proper. I may be changing the clutch over winter so I could add then. Is adding the VSS to the howell tuned comp difficult ?

Back to the posters issue, could the TPS be off ?

 

[h82crash]

P0507 is actually often CTS sensor. Try unplugging it it, clear the code and see if the p0507 goes away. It will throw a CTS code. Try the same thing with the IAC.

If it is running and driving well without the VSS then it's not the VSS. It's very 50/50 hit or miss whether you need one or not with manual/th350/400, and has never thrown a code from my experience.

Worst case you have someone tune it (you can probably pick up 10-15hp) and delete the code with HP Tuners if you don't figure it out.

It is a stock manual transmission tune on a factory PCM with rear O2, EGR and evap purge deleted. Yes, runs and drives fine, no weird behaviors.

I do not see the relationship between coolant temp and IAC RPM fault codes. I will try the unplug CTS/ECT suggestion, as it can't hurt.

But, if the crank sensor is reading 1500 rpm and the TPS says the throttle is closed, it must be MAP with high vacuum that is indicating a decel condition, and would not be initiating a P0507 code? If there is no downside, I might just turn off the MIL for P0507.

I need to get an OBDLink. Brendan did the PCM programming and retained the VSS set to 4K in case I needed it.

 

[cruisermatt]

The ECU actually does quite a lot with CTS data. Like determining open/close loop fueling for example.

Really fast and easy way to verify Crank sensor is to use a timing light or multimeter with RPM readout and compare to your scan gauge. I doubt the crank sensor is bad if it's an original early 2000's one. They usually last forever, it's just a magnet. And if there IS a crank sync issue it is almost always at high RPM only (like over 5K)

TPS is super easy to verify if you have a ScanGuage or reader. It's just a percentage of how open it is.

 

[cruisermatt]

Brendan did the PCM programming and retained the VSS set to 4K in case I needed it.

This is not the VSS we are refering to - we are talking about the sensor input TO the ECU, what you mentioned is the VSS output FROM the ECU, which is used for Cruise/speedo type stuff

 

[h82crash]

This is not the VSS we are refering to - we are talking about the sensor input TO the ECU, what you mentioned is the VSS output FROM the ECU, which is used for Cruise/speedo type stuff

Yes, I understand that. If needed, I would get a different VSS because my Dakota one is the 16K DC square wave, not compatible with the GM computer. He can change the pulse rates the PCM can accept. But, no stalling issues so, moot.

 

[h82crash]

Well, I tried some of the suggestions, took her for a drive and now have 4 fault codes and the fuel guage stopped working. Its making me hate this car. First start six weeks ago and been chasing these issues ever since. Never had this kind of trouble from a build before. I was trying to get this done and drive it to the Overland Expo, but I've given up on that idea.

 

[cruisermatt]

What codes? List them

 

[h82crash]

Been working on P0135 since before the P0507. Heater circuits on the O2 sensors check good and 12+ volts at the connectors, still throwing the code. New Bosch sensors.

P0151 is new, first time in six weeks and 100 miles of test drives.

Of course, the P0507 returned and another P0151 was pending.

My Dakota cluster was reading 1/4 tank so I stopped on the test drive and filled up. Restart and the gauge reads empty and a fuel error in the digital field.

Its disappointing after all the work I've done.

 

[cruisermatt]

you said you have four codes. What are the four codes. you only listed three.

 

[h82crash]

Been working on P0135 since before the P0507. Heater circuits on the O2 sensors check good and 12+ volts at the connectors, still throwing the code. New Bosch sensors.

P0151 is new, first time in six weeks and 100 miles of test drives.

Of course, the P0507 returned and another P0151 was pending.

My Dakota cluster was reading 1/4 tank so I stopped on the test drive and filled up. Restart and the gauge reads empty and a fuel error in the digital field.

Its disappointing after all the work I've done.

I listed four. P0151 was pending. It tripped the CEL and then failed again and stored as pending. Scan tool called it 4 codes, so I called it 4 codes. But, yes, P0151 was thrown twice.

 

[cruisermatt]

Ok, that is three codes.

Clear all the codes and swap the left and right o2 sensor plugs with each other and see what happens.

 

[h82crash]

Thanks, I can see what I can do, left harness connector will not reach the right side.

Also, the P0135 code will not go away. 12+v at the connectors for the heater circuits, no open circuits on the O2 sensors. No reason for the code. Internet says if those check good, then bad PCM.

Going to try back probing on the sensor side while connected and see if there is a major voltage drop. But, I made the harness, I know there are no corroded junctions and a solid supply from the fuse block.

 

[h82crash]

From the internet, meaning probably inaccurate:

What Are Some Causes of a P0135 Code?​

There are only two known causes that contribute to the display of a P0135 error code. The first and most common cause is the detection of a short or open circuit, or an excessive current draw in the heater circuit detected by the ECM. This code will also appear as the ECM tests for excessive current draw or opens/shorts in the O2 heater circuit when the car starts.


Rechecked both sensors. both heater circuits read 14 ohms. Back probed both while connected and both read over 12 volts under load. So, the problem is somewhere else.
This is the usual experience for me. Whenever I have a failure, it is never the common cause.

 

[h82crash]

Ok, that is three codes.

Clear all the codes and swap the left and right o2 sensor plugs with each other and see what happens.

I swapped the o2 sensors from side to side. Several starts, a short drive, so far no P0135 or P0151. Still have the P0507.