tcanin00
Well-Known Member
I got the harness ready to test, and it works!
The car runs despite my best efforts.
The car runs despite my best efforts.
OBD I to OBD II Conversion Issues
- Thread starter tcanin00
- Start date
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tcanin00
Well-Known Member
The video shows that I removed just enough of the OBD I harness to hook up the OBD II, just incase it didn't work. After the test run, I rerouted it and removed the OBD I harness.
Test drove the car and it seemed to run better at idle and low RPM. Went to drive it further the next day, and it was fine until I was on the highway for about 10 miles. It started acting like it was running out of gas, and would come back after letting off the throttle.
70 MPH is about 3,500 RPM since it has 3:73 gears and a 904.
Three codes were generated,
P0138 O2 sensor circuit high voltage
P0505 Idle control system. Listed as an SBEC II code in the FSM and required CAN/BUS diagnostics.
P1492 Battery temperature sensor fault, possibly high input voltage. I don't have the sensor, but the connector is there for it.
Would like to hear what you guys think it is.
Test drove the car and it seemed to run better at idle and low RPM. Went to drive it further the next day, and it was fine until I was on the highway for about 10 miles. It started acting like it was running out of gas, and would come back after letting off the throttle.
70 MPH is about 3,500 RPM since it has 3:73 gears and a 904.
Three codes were generated,
P0138 O2 sensor circuit high voltage
P0505 Idle control system. Listed as an SBEC II code in the FSM and required CAN/BUS diagnostics.
P1492 Battery temperature sensor fault, possibly high input voltage. I don't have the sensor, but the connector is there for it.
Would like to hear what you guys think it is.
tcanin00
Well-Known Member
Just found something interesting. In the process of rerouting some of the wiring, I cut the battery temperature sensor wires off in order to run them to the trunk where the battery is. Tried to start the car and nothing, no fuel pump prime, no relays, nothing.
So I start troubleshooting, checking connectors, grounds, wires I soldered, couldn't figure it out. Hook up the battery temperature sensor wires and it starts right up. The only thing I could think of is the temperature sensor grounds with a BK/LB sensor ground wire at the Joint Connector in the PDC, and not having it connected opened the sensor ground circuit.
So I start troubleshooting, checking connectors, grounds, wires I soldered, couldn't figure it out. Hook up the battery temperature sensor wires and it starts right up. The only thing I could think of is the temperature sensor grounds with a BK/LB sensor ground wire at the Joint Connector in the PDC, and not having it connected opened the sensor ground circuit.
tcanin00
Well-Known Member
Drove the car some more and it started cutting out around 60 MPH. When it's happening, the idle air control valve operates to try and bring the RPM's back. Trying to get off the highway it starts doing the same thing at lower speeds until it stalls. It will start back up after a few tries, but doesn't like having much throttle input.
What I've seen by using a Bluetooth OBD II data link and the Torque app is that the TPS signal has almost a second of delay between moving the throttle and showing movement percentage. The speed input is almost double actual speed. Speed input read correctly with OBD I with a Standard Motor Products part # SC108 speed sensor.
Currently showing two trouble codes:
P0138 O2 sensor circuit high voltage
P1492 Evap/Purge control circuit
My theory is that with input speed being doubled, the computer is going into speed limiter mode. I think the O2 sensor is giving a rich condition and the computer is trying to lean it out.
Let me know what you guys think.
What I've seen by using a Bluetooth OBD II data link and the Torque app is that the TPS signal has almost a second of delay between moving the throttle and showing movement percentage. The speed input is almost double actual speed. Speed input read correctly with OBD I with a Standard Motor Products part # SC108 speed sensor.
Currently showing two trouble codes:
P0138 O2 sensor circuit high voltage
P1492 Evap/Purge control circuit
My theory is that with input speed being doubled, the computer is going into speed limiter mode. I think the O2 sensor is giving a rich condition and the computer is trying to lean it out.
Let me know what you guys think.
Bobzilla
Well-Known Member
The TPS delay may not be a problem, but without another working vehicle to compare it to we would be guessing either way. TPS is slow on mine, but not that slow. I am guessing that one is a normal situation for that particular scanner setup.
The factory vehicle speed limiter is often around 112-115 and sometimes lower depending on what the PCM came out of. If yours is reading twice actual speed you are probably hitting that limiter, just as you suspected.
The factory vehicle speed limiter is often around 112-115 and sometimes lower depending on what the PCM came out of. If yours is reading twice actual speed you are probably hitting that limiter, just as you suspected.
tcanin00
Well-Known Member
The module is universal, so I could run it on my 2006 GMC Canyon to see if the TPS has the same delay.
On the subject of live data viewing, I could easily read it from the SBEC with a Snap On Solus. I can read the JTEC, but the menus are different. I need to look up more about how to use the scanner because it uses external circuit card keys the plug into the data port, and different menus used different keys.
The PCM came from a 1999 Dakota 5.2 with a manual transmission.
Bobzilla
Well-Known Member
When I get back to my computer later tonight I will try to check the menus in the PCM to see if there is a selection for setting axle ratio or tire revs per mile. I don’t remember seeing it. For now, unplug the vehicle speed sensor and drive again. See if it still cuts out.
tcanin00
Well-Known Member
Thank you for looking into this. I know the 1999 Dakota's speed input does not go directly to the PCM, it goes to the ABS Module from the VSS in the rear axle. I'll disconnect my VSS input and see what it does. I'm also running a Ford 8.8 axle that has a tone ring and an output for the ABS system. It's connected to the 1994 Dakota's RWAL module now, so I could get a speed output from there if the VSS from the transmission won't work.
Bobzilla
Well-Known Member
Wait; the rear axle speed sensor is wired in and the RWAL crap is wired in? Unplug the rear axle speed sensor.
tcanin00
Well-Known Member
The 1994 Dakota RWAL module gets a VSS from both the transmission and rear axle, but doesn't send a speed signal to the PCM.
tcanin00
Well-Known Member
Test drove the car with the VSS and O2 sensors unplugged. Was able to get up to speed without it cutting out, so that theory was confirmed. I unplugged the O2 sensor because it seemed like it was leaning out. Now it is extremely rich, not surprised. It also fumbled on acceleration, backfiring through the intake under load. I'll figure what is going on with the O2 sensor wiring and see how it runs.
tcanin00
Well-Known Member
Want to update a few things. I posted a shorter version of this thread in the Facebook group Magnum EFI Swap. One suggestion was to send the VSS output to pins 25 and 28 of C2. It didn't work for me because I have a manual transmission PCM that isn't programmed to receive a speed input from those pins.
Also rewired the O2 sensor signal wire. I haven't checked the codes yet, but it runs a lot better. Still has a slight miss at low RPM on acceleration. Also the IAC is working a lot on hard acceleration. Seems odd, and it doesn't pull as hard when the air is bypassing the throttle body.
Checked the Bluetooth OBD II module on my truck. With the key on/engine off there was a similar 1 second delay on the TPS like I saw on my car.
Also rewired the O2 sensor signal wire. I haven't checked the codes yet, but it runs a lot better. Still has a slight miss at low RPM on acceleration. Also the IAC is working a lot on hard acceleration. Seems odd, and it doesn't pull as hard when the air is bypassing the throttle body.
Checked the Bluetooth OBD II module on my truck. With the key on/engine off there was a similar 1 second delay on the TPS like I saw on my car.
fueliedart
Well-Known Member
Did you ever get the all the issues resolved? I put a 93 5.2 in my 83 Dodge Ram (5.2 feedback carb originally). It took me about 2 or 3 weeks to get everything wired, modified and installed. It took me about another week to find out why it wouldn't start. My truck was an automatic. The donor magnum was from a manual trans truck. The crank trigger sensors are different between a manual and an automatic. I went to the dealer, bought a sensor for an automatic, installed it, hit the key and it fired right up like it had never been out of commission. It made the truck a whole new beast. The power difference was unbelievable along with starting and just the increase in gas mileage. It took me about 2 hours to get the old sensor out and the new one in because of how tight everything was to the firewall, it was a fingertip procedure. If I had known I would have put studs in, in place of using bolts so I would only have had to slide the sensor over the studs and used nuts to secure it. Love seeing these installs done using MPFI.
when i do my next 1, i will put a little door down there to make the sensor accessible. i also read somewhere that if you elongate the holes, you can actually adjust the timing. not sure about that rumor though.
tcanin00
Well-Known Member
I'm still trying to get it to run right. My current theories are that it's leaning out and popping back through the intake because it has injectors from the 1994 OBD I set up that are 18.2 lb/hr, and the 1999 OBD II is supposed to have 23.2 lb/hr injectors. New injectors are on the way.
I'm also still getting an O2 sensor high voltage trouble code. The O2 sensor is from the OBD I system, so I'm sure that's part of the problem. I tried hooking up a wide band O2 sensor, but it didn't change anything. I'll order the right sensor for it after I change the injectors.
Despite all of this, I don't regret converting to EFI for the reasons that you listed. The car is so much better to drive knowing that don't have to mess with the float level, jets, or anything else.
tcanin00
Well-Known Member
Having an access panel would be great. I thought about making something for the top transmission bolts.
I read about guys slotting the holes of the crank position sensor to get some more base timing out of it. My concern would be the PCM would try to retard whatever advance is made by moving the CKP. Just an idea, without actually trying it.
autopar3000
Well-Known Member
Yes! The old crank sensor mod that was floating around the Ram and Dakota forums 20+ years ago. Apparently it can give you around 4° of more base timing. The PCM doesn't know it's happening because it's trusting that the CPS is where it's supposed to be, and Magnums don't have knock sensors. So if you do it be sure to run more octane or dial in your ear meter to listen for pinging.
I was planning to try it, but I ended up finding a Mopar Performance OBD1 PCM so I never bothered.
DionR
Well-Known Member
Do you have a FPR with a vacuum reference on the fuel rail and a return style fuel system? I don't remember the years things changed, but I think the OBD1 Dakota's had a return style fuel system with a vacuum referenced FPR while the OBD2 went to a returnless style with a constant fuel pressure. I know the '92 Dakota system I swapped into my '91 was setup as a return style, but the '95 Ram PCM I am running was returnless and had a constant fuel pressure. Could be you your fuel pressure is fluctuation when the PCM expects it to be constant and is tuned for that case.
Check to make sure you know which system the PCM you are using expects (probably returnless) and then make sure your system matches. In my case, I just popped the vacuum line off the FPR and made sure the fuel pressure was in the right range for the PCM. Works like the PCM expects because the fuel pressure is constant.
DionR, seems that everything changed around 95-96. 95 was still obd1 and 96 went to obd2. transmission's went from 3 wire in 95 to 8 wire in 96 up. i think 97 or 98 was not return hose on rail.
DionR
Well-Known Member
Seems right. I know the '96 OBD2 setup isn't the same as the '97+ OBD2 setup as well, at least for a Dakota.
The other hang up for me is I dropped a 5.9 under the '92 Dakota 5.2 wiring harness. So I wanted a 5.9 PCM to match and found one out of a 1995 full size van. That van used a returnless system, so that's what I matched including the injectors. I think the full size trucks used a different fuel system than the Dakota's, but it's been awhile. The trucks might all be returnless while the Dakota didn't go returnless until '96? Not sure.
I was more versed on this stuff when I was planning a SMPI swap on to my '74 and working on the SMPI swap into my '91 Dakota, but now that I am building a G3 swapped Duster I sold my harness and PCM and have forgotten a lot of it.
Bobzilla
Well-Known Member
Like DionR said, check fuel pressure. In an earlier post you mentioned 45 psi with key on and lower when cranking. That is not enough for the OB2 PCM. By memory, I think 50psi was the number for that PCM.
When does it pop or backfire? Only on acceleration?
autopar3000
Well-Known Member
Here's what I can say for sure...
My 1994 B350 van fuel system did not have a return. I am 90% sure only the 92 and 93 Magnums had a return system.
You could be right about the injector size. If your PCM is expecting bigger injectors and your fuel pressure is below OBD2 spec you might be way lean.
OBD1 fuel pressure spec is 35 - 45. From the 1994 service manual:
OBD2 fuel pressure spec is 49.2 psi +/- 5 psi. From the 98 service manual:
My 1994 B350 van fuel system did not have a return. I am 90% sure only the 92 and 93 Magnums had a return system.
You could be right about the injector size. If your PCM is expecting bigger injectors and your fuel pressure is below OBD2 spec you might be way lean.
OBD1 fuel pressure spec is 35 - 45. From the 1994 service manual:
OBD2 fuel pressure spec is 49.2 psi +/- 5 psi. From the 98 service manual:
tcanin00
Well-Known Member
I have an adjustable FPR in the trunk so that I wouldn't have to run a return line to the fuel rail. I know early Magnums had return style fuel systems. The 1994 Dakota organ donor was returnless.
tcanin00
Well-Known Member
The dropping fuel pressure while cranking was from the fuel pump only priming at key on and not coming back on while cranking. I can adjust fuel pressure and get it in range.
It backfires on acceleration and at low RPM high load, like going up a hill. I can take a video after I fix a fuel leak.
tcanin00
Well-Known Member
Yes, early Magnums had return style fuel systems with a vacuum referenced pressure regulator on the fuel rail.
My theory about the injectors is from watching the AFR gauge when it's misfiring. It stays relatively lean most of the time, and doesn't change when misses. I also watched the ignition timing, it didn't change during the event.
It seemed to run the best on OBD I at 45 psi. I can adjust the pressure and see what it does.
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