1996 PCED OBDI | SECTION 18: Diesel Diagnosis — 7.3L DI Engine |
W1 DIAGNOSTIC TROUBLE CODE (DTC) P1662
- P1662 will set, if the PCM detects a fault on the IDM enable circuit.
- Possible Causes:
- Open fuse.
- Open or shorted IDM enable circuit.
- IDM relay.
- PCM.
- Verify B+ at IDM relay primary circuit.
- Disconnect the IDM relay.
- Key on, engine off.
- Measure voltage between IDM relay circuit 361 (W/LB) and battery ground.
Is battery voltage present?
Yes | No |
GO to W2. | REPAIR open in Circuit 361 (W/LB). RESTORE vehicle. CLEAR DTCs and RETEST. |
W2 CHECK FOR SHORT TO GROUND
- Key off.
- Measure resistance between IDM relay Circuit 814 (W/BK) and battery ground.
Is resistance greater than 10,000 ohms?
W3 CHECK FOR SHORT TO GROUND ON CIRCUIT 814 (W/BK)
- Key off.
- Disconnect PCM.
- Measure resistance between IDM relay Circuit 814 (W/BK) and battery ground.
Is resistance greater than 10,000 ohms?
Yes | No |
REPLACE the PCM. RESTORE vehicle. CLEAR DTCs and RETEST. | REPAIR short to ground on Circuit 814 (W/BK). RESTORE vehicle. CLEAR DTCs and RETEST. |
W4 VERIFY THAT THE PCM IS ENABLING THE RELAY
- Key off.
- Measure resistance between IDM relay Circuit 814 (W/BK) and battery ground.
- Turn key on, while looking at DVOM.
Does resistance reading drop below 5 ohms?
Yes | No |
REPLACE the IDM relay. RESTORE vehicle. CLEAR DTCs and RETEST. | GO to W5. |
W5 CHECK CONTINUITY ON CIRCUIT 814 (W/BK)
- Key off.
- Install breakout box, leave PCM disconnected.
- Measure resistance between IDM relay Circuit 814 (W/BK) and PCM Test Pin 80.
Is resistance less than 5 ohms?
Yes | No |
REPLACE the PCM. RESTORE vehicle. CLEAR DTCs and RETEST. | REPAIR open in Circuit 814 (W/BK). RESTORE vehicle. CLEAR DTCs and RETEST. |
W6 DTC P1663 AND P1667 SET TOGETHER WITH OR WITHOUT P1668, CHECK FOR DTC P1662
- IDM and PCM connected.
- Key on, Engine off.
- Perform KOEO On-Demand Self Test.
Was DTC P1662 Present?
W7 CHECK MAXI FUSE
- PCM connected.
- Key on, engine off.
- Measure voltage between IDM (MAXI Fuse 27 on F-Series) or (MAXI Fuse 19 on Econoline) and battery ground.
Is battery voltage present on both sides of the fuse?
Yes | No |
GO to W8. | REPAIR short to ground on Circuit 876 (DG/LG) and REPLACE MAXI fuse. RESTORE vehicle. CLEAR DTCs and RETEST. |
W8 CHECK CIRCUIT 37 (Y)
- Key off.
- Disconnect MAXI fuse.
- Disconnect IDM relay.
- Measure resistance between IDM non-power side of fuse to IDM relay Circuit 37 (Y).
Is resistance less than 5 ohms?
Yes | No |
GO to W9. | REPAIR open on Circuit 37 (Y). RESTORE vehicle. CLEAR DTCs and RETEST. |
W9 CHECK CONTINUITY ON CIRCUIT 876 (DG/LG)
- Disconnect IDM.
- Measure resistance on Circuit 876 (DG/LG) between IDM connector Pin 14 to IDM relay.
Is resistance less than 5 ohms?
Yes | No |
GO to W10. | REPAIR open on Circuit 876 (DG/LG). RESTORE vehicle. CLEAR DTCs and RETEST. |
W10 IDM RELAY CHECK
- Install IDM relay, leave fuse disconnected.
- Key on, engine off.
- Measure resistance on Circuit 876 (DG/LG) between the non-power side of MAXI fuse to IDM connector Pin 14.
Is resistance less than 5 ohms?
Yes | No |
GO to W11. | REPLACE IDM relay. RESTORE vehicle. CLEAR DTCs and RETEST. |
W11 IDM GROUND CHECK
- Measure resistance on Circuit 574 (BK/PK) between IDM connector Pin 26 and battery ground.
Is resistance less than 5 ohms?
Yes | No |
REPLACE IDM. RESTORE vehicle. CLEAR DTCs and RETEST. | REPAIR open in IDM ground Circuit 571 (BK/PK). RESTORE vehicle. CLEAR DTCs and RETEST. |