jonathan909

If you're getting an assortment of codes thrown, it's probably a systemic fault (as suggested above) rather than anything wrong with the harness itself or any of the errors indicated. My experience with this a few years back (also on a '99 OBW, EJ25D) was that after doing a motor swap the transmission was acting really wonky e.g. the 3-4 shift points were drifting all over the place. I read the xmission controller codes, and they were telling me that there was a problem with communication between it and the ECU. So I got out the 'scope and poked around and everything looked okay, and someone on one of the other fora suggested a ground fault, and I kinda thought it a crap suggestion, but went through the TSM to spot all the under-hood grounds, and although they looked okay I reterminated all of them anyway, and the problem persisted. Ultimately, I settled on the ground not indicated in the TSM diagrams - the one on top of the intake manifold next to the coil pack. Captain Dumb@$$ had failed to tighten that one down after the motor swap. Did so and everything got better. So it's easy to say "look for bad grounds", but there's nothing like one for making crazy errors appear all over the place. That's where I'd start.

A quick search suggests that there are strongly-held feelings on the subject. My basic question is which grit I should choose if getting a silicon carbide Flex-Hone (ball hone) for glaze-breaking in the course of a rebuild. So I'd at least like that question answered, but don't have a problem with informed opinions wading in as to the relative merits of doing it.

None such noted. From what I can tell, if any of the (three) transmission speed sensors were bad, that'd be the blink-code the TCM would display. But we're not seeing any of that, just the code corresponding to this "AT load signal" from the ECM being bad. In fact, over the weekend (and misunderstanding - I think - the nature of the error message) I changed out the turbine speed sensor (for a junkyard part). Didn't make any difference. Since the voltage test on the ECM-to-TCM signal in question is indeed out of range, I'm pretty certain that the source of this fault lies in the upstream systems (the ECM and its sensors) and not in the TCM or transmission itself. At the moment we're looking at the MAP sensor - or its equivalent in the 1999 model, which is the "boost sensor" that's out on the shock tower next to the air filter. It's involved in a little conglomeration that includes two small air solenoid valves, one of which is mounted underneat the manifold. But that's just a guess, in part based on speculation that there's a typo in the 1999 diagnostic procedure...

No dents. Full disclosure: I did a block swap last summer, but took pans to support the pan with a big chunk of 2"x8" so as to distribute the load. I'm aware of the potential for damage in there. Thing is, the car ran great after the motor work. Over the next couple of months we'd occasionally get the AT oil temp light blinking while out on the highway, but eventually it became a solid fault along with the bad/hard shifting.

Well, kinda hard to tell, since I (we?) don't know exactly what "AT load signal" means. Presumably, any or all of the inputs available to the ECM. But if any of them (crank, cam, MAF, TPS, etc.) were faulty, it'd throw an OBD code, and that's not happening. The ECM seems to think everything is fine. Edit: See below - at the moment we think this may have to do with the MAP sensor, known in the '99 as the "boost sensor".

So far this one has been stumping us. EJ25 DOHC. Symptoms are bad/hard shifting and the AT OIL TEMP light flashing. No CEL or OBD codes. Did the shifter thing and got an error code 23 from the TCM - "AT LOAD SIGNAL", which goes from the ECM to the TCM. I followed the troubleshooting guide and confirmed the signal is out of range, and have checked the cabling and replaced the TCM, ECM, and MAF sensor (with junkyard parts). Nothing has changed the error or behaviour. Can anyone offer any suggestions? Thanks much.

Hi, folks - just discovered this board. I've got a '99 DOHC (Phase I) EJ25 (from my Legacy) that's got a trashed crank, but freshly machined heads. I can readily get my hands on a (year unknown) SOHC (Phase II) EJ25. Will the block swap directly in i.e. with my old manifold, heads, harnesses and hoses? Thanks much.