Jim Warman Posted March 2, 2007 Share Posted March 2, 2007 2001 F150, 4.2.... about 250,000 kms... Came in on the hook... no start - theft light flashing dimly. Boost and it starts and runs. Once it's in the shop, the cluster goes apeshit.... guages sweeping, lights flashing. Can communicate with the PCM but not the HEC. Dealer test mode (the "odo trick") wont run. Powers and grounds check good. Vehicle does not fail to start.... Cluster now working "normal" but still no comm... Replaced cluster and released truck. Two weeks later, it comes in on the hook... no start - no comm with cluster. This time, it will occasionally no start but only when it feels like it. SM forces me to order new cluster - amidst cries of "it don't feel right". Cluster came in today and I resisted the urge to slam dunk it. But, finally, I have a new symptom... no comm with PCM. Did the usual checks and came up with no ground. When I started pulling out the harnesses, I found G101 stuck to the bottom of the main harness.... Not a mark on it.... Never, in the 6 or 7 years that this truck was on the road, has this ground been attached to anything. This ground is tied in to the PCM case ground and it can only have back fed and grounded through the PCM mounting screws. Why could I communicate with the PCM and not the cluster for so long? I wish I knew. And they wonder why I drink..... Word to the wise.... stop ohming grounds.... load test them - BIG. An old sealed beam works good.... Wouldn't have helped in this case but I've had a a few stinkers in the last week or so.... I'm not getting much diesel lately, but this crap is making the 6.0 look like a cakewalk.... Quote Link to comment Share on other sites More sharing options...
Keith Browning Posted March 2, 2007 Share Posted March 2, 2007 Quote: And they wonder why I drink..... Yeah but this is the stuff that keeps it interesting! It seems we have visited the load testing grounds issue quite a few times now. The advice is priceless Quote Link to comment Share on other sites More sharing options...
Bruce Amacker Posted March 2, 2007 Share Posted March 2, 2007 Personally, I think a sealed beam is not enough unless you've got a voltmeter on it watching the V drop at the same time. Most sealed beams only draw a couple of amps tops, I have 2 blower motors I use- one draws 9 amps, the other 15 amps. Do you guys use Case Ground in datalogger? It's the difference between PCM ground and FP relay ground, measure in V. It should be damn close to zero. If it reads something, there is a bad PCM ground. I was working on a 2000 Taurus ABS complaint and happened to notice Case Ground was at 2+ volts in scan data. I mentioned it to the owner (tech, trainer, high end guy) who took the time to clean his PCM grounds and get the reading down to almost zero. Guess what? It fixed his TCC kick out complaint! Before this, the TCC would kick out after an extended highway drive of 30 miles plus. It made a believer out of him! Good Luck! Quote Link to comment Share on other sites More sharing options...
SteveS Posted April 22, 2007 Share Posted April 22, 2007 I've been using a sealed beam with both filiments burning (it was 8A when I measured, if I remember correctly) for voltage drop tests on electronic stuff. I do sometimes encounter poor connections at the backprobe and try to have an actual pin when posible. In desparation I've done short tests with an inline fuse powering one end of the circuit, purposly shorting the other end to see if it can flow enough current to blow the fuse. The problem with this test when needed for electronics circuits is getting a good connection at each end without wrecking the pins. I'm not familair with "Case Ground in Datalogger"; is that a test option on the new scan tool? I have access to NGS. Quote Link to comment Share on other sites More sharing options...
Jim Warman Posted April 22, 2007 Author Share Posted April 22, 2007 I can't say that I've seen it in every instance of data logger... but then I'm not looking for it. I do know that I've seen it... I just flipped through a few PC/EDs for different years... For F150, the last easily found mention of the PID was 96.... Man it sucks to get old... Quote Link to comment Share on other sites More sharing options...
Bruce Amacker Posted April 26, 2007 Share Posted April 26, 2007 I can't say that I've seen it in every instance of data logger... but then I'm not looking for it. I do know that I've seen it... I just flipped through a few PC/EDs for different years... For F150, the last easily found mention of the PID was 96.... Man it sucks to get old... I think it's in all 7.3 PSD's and sporadic gas vehicles. I don't think it's in 6.0/6.4. Quote Link to comment Share on other sites More sharing options...
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