ECM Problem ?????
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Member
Joined: Mar 2012
Posts: 39
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From: Richmond, Va
ECM Problem ?????
Changed oil , filter and oil pressure sending unit , cap and rotor good , wires good , plugs good , new TPS , cleaned IAC .
The problem I am experiencing is Oil Pressure Gauge will fluctuate and fall all the way down past low , I have checked wiring and replaced sending unit , when this happens there is no change in motor operation , idle remains the same and no valve train or other bearing noise what-so-ever.
Also intermittently will spit / pop back in intake at low rpm under load , sometimes runs normal and sometimes acts like extremely lean / weak with backfire through intake.
I am curious whether Oil Pressure Gauge is controlled by ECM , I have been told that these trucks suffered from gauge cluster problems as well as ECM issues , my thought is if sending unit is fed into ECM and ECM controls signal to gauge then I may very well have a ECM problem .
When cold all seems to be fine , oil pressure gauge issues seem to increase the longer truck is running indicating a possible breakdown regarding temperature , yesterday the gauge was pretty much constantly doing this fluctuating and dropping all the way , I had a friend watch and report gauge readings while I stood by motor with hood up , again with pressure dropping below "L" on gauge , there was no idle rpm change , continued running smooth , and no valve or bearing noise ....................... I find it hard to believe it would be the gauge cluster seeing that all other gauges and cluster lighting are working just fine , I am thinking that gauge is controlled by ECM via Sending Unit signal and that I have a bad ECM which may explain the other intermittent problems as well .
If anyone could give me some input on this I would greatly appreciate it .
The problem I am experiencing is Oil Pressure Gauge will fluctuate and fall all the way down past low , I have checked wiring and replaced sending unit , when this happens there is no change in motor operation , idle remains the same and no valve train or other bearing noise what-so-ever.
Also intermittently will spit / pop back in intake at low rpm under load , sometimes runs normal and sometimes acts like extremely lean / weak with backfire through intake.
I am curious whether Oil Pressure Gauge is controlled by ECM , I have been told that these trucks suffered from gauge cluster problems as well as ECM issues , my thought is if sending unit is fed into ECM and ECM controls signal to gauge then I may very well have a ECM problem .
When cold all seems to be fine , oil pressure gauge issues seem to increase the longer truck is running indicating a possible breakdown regarding temperature , yesterday the gauge was pretty much constantly doing this fluctuating and dropping all the way , I had a friend watch and report gauge readings while I stood by motor with hood up , again with pressure dropping below "L" on gauge , there was no idle rpm change , continued running smooth , and no valve or bearing noise ....................... I find it hard to believe it would be the gauge cluster seeing that all other gauges and cluster lighting are working just fine , I am thinking that gauge is controlled by ECM via Sending Unit signal and that I have a bad ECM which may explain the other intermittent problems as well .
If anyone could give me some input on this I would greatly appreciate it .
Last edited by n4ynu1010; Apr 14, 2012 at 11:40 AM. Reason: Typo
Senior Member
Joined: Feb 2009
Posts: 709
Likes: 31
From: Grants Pass, OR
We are talking about an '89 5.0? Found in your profile.
Is the fuel gauge and coolant temp gauges acting up as well? They are all 3 powered by the same voltage regulator in the instrument panel. The voltage regulator pulses 5VDC every half a second.
There is no connection at all to the EEC.
http://img855.imageshack.us/img855/8410/instrurment.jpg
Is it throwing any codes?
See link in my signature on how to run self test / retrieve codes
Is the fuel gauge and coolant temp gauges acting up as well? They are all 3 powered by the same voltage regulator in the instrument panel. The voltage regulator pulses 5VDC every half a second.
There is no connection at all to the EEC.
http://img855.imageshack.us/img855/8410/instrurment.jpg
Is it throwing any codes?
See link in my signature on how to run self test / retrieve codes