[Carl M.]

Have a 96 f250 7.3 Injector Driver module fail code number p1668. Before the no start I was getting a P1298 code also. The testing diagrams say if you have both the IDM has to be replaced. So wondering where to get one and if its worth it to get an upgraded one. I have a TW 6pos chip I tried taking out and then starting it but still didnt budge. Not even a hiccup.

 

[Patrick Feeley]

I've had success getting a couple off ebay for $50 each. Your results may vary if you choose that route. Any IDM from a 1994-2003 7.3 PSD will work. If you do choose the "upgraded" route, go with the Swamps High Frequency unit (reviews on that unit have been positive on the forums). Cheers!

 

[Carl M.]

Found the real problem

So i got my new IDM from Neet Computers for $140. I put it in and now I have 3 new codes. P1278 Cylinder No 8 high to low side open. P1293 and 1294. Open circuit. Since the scanner reads open circuits on both banks you think its further back on the wiring harness?

 

[klhansen]

If you didn't mess with the wiring connectors at the valve covers, then recheck the connector at the IDM itself. I was testing one once and gooped too much dielectric grease on the connection and it threw a bunch of codes. Once I wiped off the excess, it was good to go.

If that doesn't work, check the connections at the valve covers and use an ohmmeter to check continuity thru the injector solenoids.

If everything checks out OK, then send the IDM back and get another one.

 

[bugman]

Here is some information on testing the injectors and wiring from the IDM plug

 

[Carl M.]

Ok i Checked all the pins on the idm plug and all the injectors are showing 3.7 ohms and it still doesnt start its still showing the same three codes. So i sent the idm back.

 

[Carl M.]

So I got my 2nd idm and still no start not even a hiccup. Still has 1293 and 1294 codes which are Banks 1 and 2 open circuit. Not sure wat to do next...

 

[Patrick Feeley]

Just to verify, you are clearing the existing codes, yes? Anyway, here are the pinpoint tests for P1293 and P1294 from the Powertrain Control/Emissions Diagnosis (PC/ED) Manual:

AB20 DIAGNOSTIC TROUBLE CODES (DTCs) 1293 AND 1294: CHECK FOR VOLTAGE ON HIGH SIDE CIRCUIT
DTCs 1293 and 1294 indicate an open circuit exists on the high side circuit between the IDM and the injectors. The following table lists the circuits to inspect while performing these pinpoint tests, based on the DTC retrieved during the KOEO On-Demand and Injector Electrical Self Tests.

DTC / High Side / Injector Bank
1293 / 1087 (O) / Right
1294 / 878 (PK/Y) / Left

Key off.
Disconnect both connectors on the bank with the code.
Key on, engine off.
Measure voltage on the suspect high side circuit Pin C on the injector vehicle harness connectors to battery ground.
Is battery voltage present?

Yes: GO to AB21
No: GO to AB24

AB21 CHECK INJECTOR RESISTANCE
Key off.
Suspect injector valve cover connectors disconnected.
Install Rotunda Glow Plug Injector Adapter 014-00935 or equivalent.
Measure resistance between high side and low side injector terminals on the adapter tool.
Is resistance less than 5 ohms?

Yes: Fault may be intermittent. GO to AB15
No: GO to AB22

AB22 CHECK HARNESS FOR OPEN
Remove valve cover.
Disconnect injector harness connector.
Measure resistance between injector connector and exterior gasket connector.
Is resistance less than 5 ohms?

Yes: REPLACE injector. RERUN Scan Tool Diagnostic Test
No: GO to AB23

AB23 DETERMINE WHETHER GASKET OR UVC HARNESS HAS FAILED
Disconnect UVC harness from gasket.
Measure resistance across each contact in the gasket.
Is each resistance reading less than 5 ohms?

Yes: REPLACE UVC harness
No: REPLACE valve cover gasket

AB24 CHECK FOR OPEN IN HIGH SIDE CIRCUIT
Key off.
Disconnect IDM.
Both connectors on the bank with the code disconnected.
Using a DVOM and the flex tips supplied with the NGS Tester, measure resistance on the suspect high side circuit at the IDM connector to Pin C on both suspect injector connectors.
Are both resistance readings less than 5 ohms?

Yes: Fault may be intermittent. GO to AB15
No: REPAIR open in high side circuit

AB15 CHECK FOR OPEN INJECTOR CIRCUIT
Key off.
IDM disconnected.
All other connectors plugged in.
Using a DVOM and flex tips supplied with the NGS Tester, measure resistance between suspect low side to high side circuit at the IDM connector. Refer to injector illustration at beginning of this pinpoint test for pin location.
Grasp the harness close to the suspect injector harness connector. Wiggle, shake harness while working your way back to the IDM.
Do resistance readings ever go above 5 ohms?

Yes: ISOLATE open in circuit and REPAIR
No: IDM internal failure. REPLACE IDM

Hope that helps, but I'm not sure if those will provide anything new. Cheers!

 

[Carl M.]

Ok so looks like i also had a bad cps. I replaced it a month or 2 ago but i wasnt a dealer cps so thats probly why it went bad. Got one from the dealer and put it in and it started right up! thanx for all the help i love diesel forums!!!!!!!!

 

[Kimber1911]

Ok so looks like i also had a bad cps. I replaced it a month or 2 ago but i wasnt a dealer cps so thats probly why it went bad. Got one from the dealer and put it in and it started right up! thanx for all the help i love diesel forums!!!!!!!!

Glad you got it fixed.

In my humble opinion, a trouble code alone should never be the basis for a parts purchase.