sondogg12 Posted June 26, 2008 Share Posted June 26, 2008 school bus.dies at stop.restarts fine all the time.cmp replaced.only code p1670.what have you guys seen out there.Any known concerns? Quote Link to comment Share on other sites More sharing options...
Keith Browning Posted June 26, 2008 Share Posted June 26, 2008 One of my all time favorites. /forums/images/%%GRAEMLIN_URL%%/eek.gif This code and symptom is related to the communications between the PCM and the IDM. The diagnostics for this code are somewhat ambiguous should the fuel delivery command signal and electronic feedback circuits test good. At the end, depending on whether there are codes or not and where the codes are you either replace the PCM or the IDM. My experience has been frustratingly mixed, not one had a circuit issue and more than half of the time I replaced the wrong module at the manual's instruction. If you can duplicate the concern fairly regularly I suggest you try swapping the IDM and PCM, one at a time with known good modules from a like vehicle. Being a bus I would guess it's from a fleet and a donor vehicle might be readily available... 'specially since school is out for the summer! /forums/images/%%GRAEMLIN_URL%%/wink.gif That reminds me, this is when I usually get hit with all the shit work the local bus fleets can't get to - eeeesh! /forums/images/%%GRAEMLIN_URL%%/sick.gif Good Luck Quote Link to comment Share on other sites More sharing options...
Bruce Amacker Posted June 26, 2008 Share Posted June 26, 2008 One of my all time favorites. /forums/images/%%GRAEMLIN_URL%%/eek.gif This code and symptom is related to the communications between the PCM and the IDM. The diagnostics for this code are somewhat ambiguous should the fuel delivery command signal and electronic feedback circuits test good. At the end, depending on whether there are codes or not and where the codes are you either replace the PCM or the IDM. My experience has been frustratingly mixed, not one had a circuit issue and more than half of the time I replaced the wrong module at the manuals instruction. If you can duplicate the concern fairly regularly I suggest you try swapping the IDM and PCM, one at a time with known good modules from a like vehicle. Being a bus I would guess it's from a fleet and a donor vehicle might be readily available... 'specially since school is out for the summer! /forums/images/%%GRAEMLIN_URL%%/wink.gif That reminds me, this is when I usually get hit with all the shit work the local bus fleets can't get to - eeeesh! /forums/images/%%GRAEMLIN_URL%%/sick.gif Good Luck Have you checked fuel pressure and sampled it to verify good clean fuel? I agree with Keith on all counts, but have seen the P1670 be a ghost code also, so keep in mind that your problem may lie in the PCM/IDM communications, but may also be elsewhere. I'd go for a road test with a fuel pressure gauge and monitor/graph ICP voltage to satisfy myself. Scoping circuit 818 on a RT is probably a good idea, too. Don't overlook the basics! Also, I'd backprobe the IDM power and ground circuits and verify you're getting good power and ground to the unit. The IDM power relay is definitely a pattern failure item and could set this code if it had high resistance. Is it a '99 model year? There's an updated IDM to get rid of this code. Here's some copies from my book on this topic, and some known good waveforms from a '99 if you're a scope dude: The PCM generates two signals for the IDM from the cam sensor signal, the FDCS (Fuel Delivery Command Signal) and the CID (Cylinder Identification Signal). The IDM generates a return message via the IDM return circuit. The messages include whether the proper fuel and timing signals were received, and the IDM also communicates injector circuit problems via the return circuit. The FDCS (Fuel Delivery Command Signal) includes basic information from the PCM to the IDM on fuel pulse width and timing. This signal consists of a 14v digital square wave at 43 hz at an idle. The CID (Cylinder Identification Signal) is a synchronizer signal to identify what cylinder should be fired. It consists of a 14v digital square wave at 5.4 hz at an idle. The IDM generates a return message which consists of a 11.2v digital square wave at about 41hz (idle). The messages include whether the proper fuel and timing signals were received, and the IDM also communicates injector circuit problems via the return message. IDM return codes are common and are treated with a new IDM per TSB. Check your power and ground first! Good Luck! /forums/images/%%GRAEMLIN_URL%%/grin.gif Quote Link to comment Share on other sites More sharing options...
sondogg12 Posted June 27, 2008 Author Share Posted June 27, 2008 wow.good info guys.Yea the school buses are just rolling in.Yippi.Powers and grounds all good.fuel pressure and quality good.f-series idm okay to swap in e seriees.its a 99 Quote Link to comment Share on other sites More sharing options...
Keith Browning Posted June 27, 2008 Share Posted June 27, 2008 Wow, thats some good info there Bruce. I also have seen that code as a ghost... clear it and never hear of, or see the truck again. Mostly when that occurs it accompanies cam sensor codes from my observation. Quote Link to comment Share on other sites More sharing options...
Bruce Amacker Posted June 27, 2008 Share Posted June 27, 2008 f-series idm okay to swap in e seriees.its a 99 If it's a '99 I'm going to guess that your stalling complaint is likely not related to the P1670. Yes, you can swap IDMs without trouble. Double check your FP and quality and swap in a known good ICP. A biased ICP will cause this. Good Luck! /forums/images/%%GRAEMLIN_URL%%/grin.gif Quote Link to comment Share on other sites More sharing options...
Mekanik Posted June 28, 2008 Share Posted June 28, 2008 I feel like an idiot for posting this because I know this is a school bus, but I seem to remember having a stalling 7.3L Excursion with a p1670 that was caused by a chip in the pcm. I would probably swap a known good IDM first. I have replaced many IMDs in 7.3Ls. Quote Link to comment Share on other sites More sharing options...
sondogg12 Posted June 29, 2008 Author Share Posted June 29, 2008 Just dies without warning.doesnt stumble then die.Fuel pressure good and quality good.ill try monday with the idm. Quote Link to comment Share on other sites More sharing options...
sondogg12 Posted June 29, 2008 Author Share Posted June 29, 2008 Just dies without warning.doesnt stumble then die.Fuel pressure good and quality good.ill try monday with the idm. Quote Link to comment Share on other sites More sharing options...
sondogg12 Posted July 3, 2008 Author Share Posted July 3, 2008 TSB 03-21-32 HARD START/LONG CRANK - VEHICLES EQUIPPED WITH AFTERMARKET MODIFICATIONS AND 7.3L DIESEL ENGINE Publication Date: October 7, 2003 FORD: 1997-1999 ECONOLINE Article 98-26-9 is being republished in its entirety as part of a consolidated 7.3L diagnostic aid booklet. ISSUE: Some vehicles equipped with aftermarket modifications may exhibit a crank but no start or a hard start/long crank condition. Some 7.3L Econolines with aftermarket modification to the electrical systems may exhibit "chattering" of the Injector Driver Module (IDM) relay. This may be caused by modifications to the vehicle which may not provide enough electrical current to maintain the function of the IDM relay. ACTION: Run a dedicated power source to Pin 85 of the IDM relay. This action will isolate the IDM relay power circuit from any circuits that may have aftermarket equipment connected to them. Refer to the following Service Procedure for details. SERVICE PROCEDURE Check for 12V at Pin 87, Circuit 876 in Start or Run, and during cranking. If 12V is present in Start, Run, and during cranking, proceed with normal diagnostics. If 12V is not maintained during cranking, proceed to Step 2. Check Powertrain Control Module (PCM) ground wire connection for corrosion or poor contact. Ground in the circuit is G101 on Page 151-10 at location E1 in the 1998 and 1999 Econoline Electrical and Vacuum Troubleshooting Manual (EVTM). Ensure proper contact. If concern is not resolved, perform Step 3. Run a 10 gauge wire from the starter motor relay post (Battery +) to the engine compartment fuse box. Install a 30 amp sealed fuse in the 10 gauge wire. Cut the wire that attaches to Pin 85 of the IDM relay (Relay F) in the engine compartment fuse box ensuring that enough wire is left to splice in the new 10 gauge wire from Step 2. The wire to be cut is Circuit 361 (non-electric fuel pump) or Circuit 16 (electric fuel pump). Attach the new 10 gauge wire to Circuit 361 (non-electric fuel pump) or Circuit 16 (electric fuel pump) using solder and heat shrink tubing. Cover the unused end of Circuit 361 or Circuit 16 with heat shrink tubing to prevent shorts. Secure all wiring and test vehicle ensuring that 12V is present at Pin 87, Circuit 876 in Start, Run, and during cranking Somebody performed this tsb due to this issue above.there dedicated 12v supply was building corrosion.i just jumper it to another 12v hot at all times.fixed it. Thanks for your help everyone. Quote Link to comment Share on other sites More sharing options...
Keith Browning Posted July 3, 2008 Share Posted July 3, 2008 Somebody performed this TSB due to this issue above. Their dedicated 12V supply was building corrosion. I just jumper it to another 12V hot at all times. Fixed it. Good find - Good job! /forums/images/%%GRAEMLIN_URL%%/thumbup.gif Quote Link to comment Share on other sites More sharing options...
lmorris Posted March 20, 2017 Share Posted March 20, 2017 All good information to have on hand. I have one that will idle on the runway between flights all day, the idle will surge then it quits. P1670 is the only code. After reading this I checked the ICP sensor and found the connector full of oil. Quote Link to comment Share on other sites More sharing options...
garyb Posted April 22, 2017 Share Posted April 22, 2017 I have a 200 f-250 that sets p1668-ef signal pcm-idm err. load test power and grounds to idm, and passed, check continuity on communication ckts. between pcm and idm, .3ohms, check ckts. for short to grnd, and short to pwr. no problem found, injectors will not buzz with this dtc, replaced idm, and seamed like all ok, injectors buzzed and truck start and run for about 20 minutes, then stalled, performed self test again, and new idm set p1668, performed service parts replacement of idm, truck starts and runs and within a few minutes will stall again and get same hard fault, p1668, and same symptom no buzz of injectors and crank no start. beginning to thank pcm concern at this point. good info in this post. Quote Link to comment Share on other sites More sharing options...
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