sgauvry Posted February 11, 2018 Author Share Posted February 11, 2018 Steve, any ECM 1987-1993 I believe for a 5.0L engine and AOD transmission will work fine on yours. Changes to use a later ECM. EGR changed from two solenoid valves (one vacuum and one vent) to a single duty cycle solenoid valve. MAP sensor, PN changed in 1987, I don't know exactly what changed and have used a later one on a 1986 truck. Speed sensor, 1987 up have a speed sensor input, readily available item, becomes the speedometer gear holder and uses two wires to the ECM. Air filter, 1987-1997 the filter is moved to a location on the left fender behind the radiator/washer tank, air is still taken from the rectangular hole on the left side of the radiator. Improvements: TPS is no longer extremely voltage sensitive requiring a setting to 1.0 volt at closed throttle +/- a very small tolerance, 1987 up, the closed throttle voltage is measured by the ECM and used as base value, minimum idle speed is set with the IAC disconnected to a specified RPM. Newer MAP sensor was used from 1987-1997 on non-OBD-II trucks, is easier to find. Newer EGR control solenoid is also used on many other applications and easy to locate. Speed input allows ECM to tailor parameters better, EGR for one. After a point, and I will have to find it, ECM can deliver live data to a good scan tool so actual functions, advance, idle air flow, engine temperature, air charge temperature, EGR %, throttle % can be viewed for diagnostic purposes. Wiring, speed sensor wiring needs to be added, EGR reconfigured. Gary has a spreadsheet I sent him with the truck ECM pinouts. Starting in 1987 the engine harness was completely changed, it connects to the front harness with 4 round, weatherproof 8 pin plugs. The ECM connection is part of the front harness, no longer a "piggy back" system as the ECM was moved to the left air box in a recess. ECM power relay and fuel pump relay were also moved from inside the cab to a bracket on the rear of the new air filter location. Some of these you may not want to fool with, the others, your call, it's your truck! Wow! That is ALL significant. I especially like this: "TPS is no longer extremely voltage sensitive requiring a setting to 1.0 volt at closed throttle +/- a very small tolerance, 1987 up, the closed throttle voltage is measured by the ECM and used as base value, minimum idle speed is set with the IAC disconnected to a specified RPM." I'll have to give this some thought and may pursue it. I figure I might as well go all the way if I make the change, but may need some tutoring. I'll also confer with Gary when I'm ready to undertake those changes and ask him to share his spreadsheet. Thanks!! Link to comment Share on other sites More sharing options...
sgauvry Posted February 11, 2018 Author Share Posted February 11, 2018 Steve, any ECM 1987-1993 I believe for a 5.0L engine and AOD transmission will work fine on yours. Changes to use a later ECM. EGR changed from two solenoid valves (one vacuum and one vent) to a single duty cycle solenoid valve. MAP sensor, PN changed in 1987, I don't know exactly what changed and have used a later one on a 1986 truck. Speed sensor, 1987 up have a speed sensor input, readily available item, becomes the speedometer gear holder and uses two wires to the ECM. Air filter, 1987-1997 the filter is moved to a location on the left fender behind the radiator/washer tank, air is still taken from the rectangular hole on the left side of the radiator. Improvements: TPS is no longer extremely voltage sensitive requiring a setting to 1.0 volt at closed throttle +/- a very small tolerance, 1987 up, the closed throttle voltage is measured by the ECM and used as base value, minimum idle speed is set with the IAC disconnected to a specified RPM. Newer MAP sensor was used from 1987-1997 on non-OBD-II trucks, is easier to find. Newer EGR control solenoid is also used on many other applications and easy to locate. Speed input allows ECM to tailor parameters better, EGR for one. After a point, and I will have to find it, ECM can deliver live data to a good scan tool so actual functions, advance, idle air flow, engine temperature, air charge temperature, EGR %, throttle % can be viewed for diagnostic purposes. Wiring, speed sensor wiring needs to be added, EGR reconfigured. Gary has a spreadsheet I sent him with the truck ECM pinouts. Starting in 1987 the engine harness was completely changed, it connects to the front harness with 4 round, weatherproof 8 pin plugs. The ECM connection is part of the front harness, no longer a "piggy back" system as the ECM was moved to the left air box in a recess. ECM power relay and fuel pump relay were also moved from inside the cab to a bracket on the rear of the new air filter location. Some of these you may not want to fool with, the others, your call, it's your truck! I reread your post this morning. Are you saying that if I utilize a 1987 ECM, I'll have to use a 1987 or up harness? Or is it possible to use the 86 harness I just got from Ray, with a few modifications? I'd like to take advantage of the following: 1. Advantages of a less sensitive TPS 2. MAP sensor - Will my present MAP sensor work pr must I upgrade to a newer version? 3. Newer EGR control solenoid - although I'm not certain what that entails in terms of reconfiguration. I want to utilize the harness I got from Ray. And it seems to me that each of the above three improvements are things that work in tandem with each other, so making improvement on one wouldn't make sense unless all three improvements are made. Correct? Thanks!! Steve Link to comment Share on other sites More sharing options...
NotEnoughTrucks Posted February 12, 2018 Share Posted February 12, 2018 I reread your post this morning. Are you saying that if I utilize a 1987 ECM, I'll have to use a 1987 or up harness? Or is it possible to use the 86 harness I just got from Ray, with a few modifications? I'd like to take advantage of the following: 1. Advantages of a less sensitive TPS 2. MAP sensor - Will my present MAP sensor work pr must I upgrade to a newer version? 3. Newer EGR control solenoid - although I'm not certain what that entails in terms of reconfiguration. I want to utilize the harness I got from Ray. And it seems to me that each of the above three improvements are things that work in tandem with each other, so making improvement on one wouldn't make sense unless all three improvements are made. Correct? Thanks!! Steve Steve, at a very quick glance, I don't see any wiring changes between the 85/86 ECU and the later ECU's. That said, you would have to stay away from any ECU application that also controlled an electronically shifted transmission.For most features, the 85/86 wiring harness would be fine. I think Bill has mentioned a different MAP sensor and should you choose an ECU that supports live data monitoring, I believe you would have to add the extra wires. For the greatest part though, I think you should be able to adapt any SD EECIV ECU. I have some Haynes level drawings that help to compare the pinouts. I'll send them to you by email. Link to comment Share on other sites More sharing options...
85lebaront2 Posted February 12, 2018 Share Posted February 12, 2018 Steve, at a very quick glance, I don't see any wiring changes between the 85/86 ECU and the later ECU's. That said, you would have to stay away from any ECU application that also controlled an electronically shifted transmission.For most features, the 85/86 wiring harness would be fine. I think Bill has mentioned a different MAP sensor and should you choose an ECU that supports live data monitoring, I believe you would have to add the extra wires. For the greatest part though, I think you should be able to adapt any SD EECIV ECU. I have some Haynes level drawings that help to compare the pinouts. I'll send them to you by email. There are differences, first because the 1985.5-1986 EGR system is different from later ones, second, no speed input on the early ones, third, no brake switch input, VPWR is on pin #5 and pin #57, later only on pin #57. Link to comment Share on other sites More sharing options...
Gary Lewis Posted February 12, 2018 Share Posted February 12, 2018 There are differences, first because the 1985.5-1986 EGR system is different from later ones, second, no speed input on the early ones, third, no brake switch input, VPWR is on pin #5 and pin #57, later only on pin #57. I have an '87 EVTM if y'all need pages from it. Link to comment Share on other sites More sharing options...
NotEnoughTrucks Posted February 13, 2018 Share Posted February 13, 2018 Steve, at a very quick glance, I don't see any wiring changes between the 85/86 ECU and the later ECU's. That said, you would have to stay away from any ECU application that also controlled an electronically shifted transmission.For most features, the 85/86 wiring harness would be fine. I think Bill has mentioned a different MAP sensor and should you choose an ECU that supports live data monitoring, I believe you would have to add the extra wires. For the greatest part though, I think you should be able to adapt any SD EECIV ECU. I have some Haynes level drawings that help to compare the pinouts. I'll send them to you by email. Going to revise my guess. There certainly are differences. Did a spreadsheet. If live data is what you are after, 92 and later ECUs should work. Looks like some 6 cyl applications got it in 90/91. Key to look for is in the EEC test connector to see if it has the two extra wires. DLC +/- in the spreadsheet attached. PDF and OpenOffice formats attached. I saw somewhere that this data is in an RS485 format. Possibly it could be read with a terminal program? Year_comparisons_SD.pdf Year_comparisons_SD.ods Link to comment Share on other sites More sharing options...
Gary Lewis Posted February 13, 2018 Share Posted February 13, 2018 Going to revise my guess. There certainly are differences. Did a spreadsheet. If live data is what you are after, 92 and later ECUs should work. Looks like some 6 cyl applications got it in 90/91. Key to look for is in the EEC test connector to see if it has the two extra wires. DLC +/- in the spreadsheet attached. PDF and OpenOffice formats attached. I saw somewhere that this data is in an RS485 format. Possibly it could be read with a terminal program? Year_comparisons_SD.pdf Year_comparisons_SD.ods You guys are doing a lot of work on this! I am impressed. But, won't there be a lot of electrical rewiring to use a later ECU/PCM? Or, is it just adding a few wires and changing out the ECU? And, any idea what ECU's? Just any '92 and later? Won't it have to be a 5.0L? Link to comment Share on other sites More sharing options...
NotEnoughTrucks Posted February 13, 2018 Share Posted February 13, 2018 You guys are doing a lot of work on this! I am impressed. But, won't there be a lot of electrical rewiring to use a later ECU/PCM? Or, is it just adding a few wires and changing out the ECU? And, any idea what ECU's? Just any '92 and later? Won't it have to be a 5.0L? Pretty much what Bill said a few posts up. Of course, it would have to be a compatible drivetrain. Anyways, staying up late and it's still too cold to have any fun outside, so I color coded the compatibility. I think an 87/89 ECU would be a relatively easy swap.Only a few functions to repin, delete some EGR functions and add a VSS circuit. Might be an issue if the diff does not have the tone ring! Revised spreadsheet. SD_compatibility.pdf Year_comparisons_SD_compatibility.ods Link to comment Share on other sites More sharing options...
sgauvry Posted February 13, 2018 Author Share Posted February 13, 2018 Pretty much what Bill said a few posts up. Of course, it would have to be a compatible drivetrain. Anyways, staying up late and it's still too cold to have any fun outside, so I color coded the compatibility. I think an 87/89 ECU would be a relatively easy swap.Only a few functions to repin, delete some EGR functions and add a VSS circuit. Might be an issue if the diff does not have the tone ring! Revised spreadsheet. SD_compatibility.pdf Year_comparisons_SD_compatibility.ods Nice work! Thanks!! Link to comment Share on other sites More sharing options...
85lebaront2 Posted February 13, 2018 Share Posted February 13, 2018 Nice work! Thanks!! I just sent Gary a spreadsheet with much the same information, but only went to 1987 primarily to show the differences between the 1985-86 and later versions. Other than the EGR and speed sensor additions there was a change on pin #5 from 12V in when the key is on to a ground connection tied to the speed sensor. Link to comment Share on other sites More sharing options...
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