Injector Driver Circuit Operation

1996 PCED OBDI

SECTION 18: Diesel Diagnosis — 7.3L DI Engine

AB: Injector Driver Circuit Operation

AB1 DIAGNOSTIC TROUBLE CODES (DTCs) 0261, 0264, 0267, 0270, 0273, 0276, 0279, 0282: CHECK FOR GROUND SHORT IN LOW SIDE CIRCUIT

DTCs below indicate a low side ground short in the circuit between the IDM and the injector. The following table lists the circuit to inspect while performing these pinpoint tests, based on the DTC retrieved during the KOEO On-Demand or Injector Electrical Self Tests.

Cyl.	DTC	Circuit	Cyl.	DTC	Circuit
1	0261	555 (T)	5	0273	559 (T/BK)
2	0264	556 (W)	6	0276	560 (LG/O)
3	0267	557 (BR/Y)	7	0279	561 (T/R)
4	0270	558 (BR/LB)	8	0282	562 (LB)

Key off.
Disconnect injector valve cover connector at the suspect injector.
Measure resistance from the suspect circuit of the engine harness connector to battery negative post.

Is resistance greater than 10,000 ohms?

Yes	No
GO to AB2.	GO to AB4.

AB2 CHECK SHORT IN CIRCUIT TO GROUND

Install Rotunda Glow Plug Injector Adapter 014-00935 or equivalent to the valve cover gasket.
Measure resistance on the suspect circuit to battery ground.

Is the resistance greater than 10,000 ohms?

Yes	No
Fault may be intermittent, GO to AB5.	GO to AB3.

AB3 UNDER VALVE COVER SHORT

Remove valve cover and disconnect injector connector.
Inspect under valve cover (UVC) harness for shorting to ground.

Is fault indicated?

Yes	No
REPLACE UVC harness.	REPLACE injector.

AB4 CHECK FOR SHORT BETWEEN INJECTOR VALVE COVER CONNECTOR AND IDM

Key off.
Disconnect IDM.
At IDM harness connector, measure resistance from the respective injector circuit to all other circuits in the IDM harness connector and to chassis ground.

Is the resistance greater than 10,000 ohms?

Yes	No
REPLACE IDM. RERUN Scan Tool Diagnostic Test.	SERVICE short to ground between injector valve cover connector and IDM connector. RERUN Scan Tool Diagnostic Test.

AB5 CHECK FOR INTERMITTENT SHORT TO GROUND

Key off.
Disconnect IDM. Inspect for damaged or pushed-out pins.
All other connectors plugged in.
Using a DVOM and the flex tips supplied with the NGS Tester, measure resistance between the suspect injector low side circuit on the IDM connector to battery ground post. Refer to injector illustration at beginning of this pinpoint test for pin location.
Grasp the harness close to the suspect injector connector. Wiggle, shake harness while working towards the IDM.

Does resistance ever drop below 10,000 ohms?

Yes	No
ISOLATE short to ground and REPAIR. CLEAR DTC and RETEST.	IDM internal failure, REPLACE IDM.

AB6 DIAGNOSTIC TROUBLE CODES (DTCs) 0262, 0265, 0268, 0271, 0274, 0277, 0280, 0283 and 1261-1268: CHECK FOR SHORT TO B+ OR TO HIGH SIDE IN THE LOW SIDE CIRCUIT

DTCs 1261-1268 indicate that the low side circuit is shorted to B+ or the high side circuit between the IDM and the injector. The following table lists the circuits to inspect while performing these pinpoint tests, based on the DTC retrieved during the KOEO On-Demand or Injector Electrical Self Tests.

Cyl.	DTC	Low Side	High Side
1	1261-0262	555 (T)	1087 (O)
2	1262-0265	556 (W)	878 (PK/Y)
3	1263-0268	557 (BR/Y)	1087 (O)
4	1264-0271	558 (BR/LB)	878 (PK/Y)
5	1265-0274	559 (T/BK)	1087 (O)
6	1266-0277	560 (LG/O)	878 (PK/Y)
7	1267-0280	561 (T/R)	1087 (O)
8	1268-0283	562 (LB)	878 (PK/Y)

Key on/engine off.
Disconnect IDM.
Disconnect both connectors on the bank with the code.
Measure resistance between the low side to battery positive post, then to high side at the injector valve cover connector. Refer to injector illustration at beginning of this pinpoint test for pin location.

Are both resistance readings less than 10,000 ohms?

Yes	No
GO to AB7.	REPAIR short in circuits between IDM and injector valve cover connector. RERUN Scan Tool Diagnostic Test.

AB7 CHECK FOR SHORT INTERNAL TO VALVE COVER

Key off.
Install Rotunda Glow Plug Injector Adapter 014-00935 or equivalent to valve cover gasket.
Measure resistance between high side to low side circuits.

Is resistance less than 2.0 ohms on a cold engine?

Yes	No
GO to AB8.	Fault may be intermittent. GO to AB10.

AB8 CHECK FOR SHORT UNDER VALVE COVER

Key off.
Remove valve cover.
Disconnect injector connector.
Measure resistance between Rotunda Glow Plug Injector Adapter 014-00935 or equivalent to the injector connector on both high and low side circuits.

Is resistance greater than 10,000 ohms?

Yes	No
REPLACE injector. RERUN Scan Tool Diagnostic Test.	GO to AB9.

AB9 GASKET HARNESS OR UVC SHORT LOW SIDE TO HIGH SIDE

Remove UVC harness.
Measure resistance of the gasket harness low side to high side circuitry.

Is resistance less than 5 ohms?

Yes	No
REPLACE gasket harness. RERUN Scan Tool Diagnostic Test.	REPLACE UVC harness. RERUN Scan Tool Diagnostic Test.

AB10 CHECK FOR INTERMITTENT LOW SIDE SHORT TO B+ OR HIGH SIDE

Key on/engine off.
IDM disconnected.
All four valve cover connectors disconnected.
Using a DVOM and the flex tips supplied with the NGS Tester, measure resistance between the suspect injector low side circuit to battery positive post then to high side circuit on the IDM connector. Refer to injector illustration at beginning of this pinpoint test for pin location.
Grasp the harness close to the suspect injector connector. Wiggle, shake harness while working towards the IDM.

Do either resistance readings ever drop below 10,000 ohms?

Yes	No
ISOLATE shorted circuit and REPAIR. CLEAR DTCs and RETEST.	IDM internal failure. REPLACE IDM.

AB11 DIAGNOSTIC TROUBLE CODES (DTCs) 1271-1278: CHECK FOR OPEN BETWEEN INJECTOR HIGH SIDE TO LOW SIDE AT VALVE COVER CONNECTOR

DTCs 1271-1278 indicate a low side to high side open in the circuit between the IDM and the injector. The following table lists the circuits to inspect while performing these pinpoint tests, based on the DTC retrieved during the KOEO On-Demand or Injector Electrical Self Tests.

Note: If all of the DTCs associated with an entire bank are retrieved, the high side circuit is most likely open.

Cyl.	DTC	Low Side	High Side	Bank
1	1271	555 (T)	1087 (O)	Right
2	1272	556 (W)	878 (PK/Y)	Left
3	1273	557 (BR/Y)	1087 (O)	Right
4	1274	558 (BR/LB)	878 (PK/Y)	Left
5	1275	559 (T/BK)	1087 (O)	Right
6	1276	560 (LG/O)	878 (PK/Y)	Left
7	1277	561 (T/R)	1087 (O)	Right
8	1278	562 (LB)	878 (PK/Y)	Left

Key off.
Disconnect injector valve cover connector.
Install Rotunda Glow Plug Injector Adapter 014-00935 or equivalent to valve cover gasket.
Measure resistance between the high side to low side on the injector. Refer to injector illustration at beginning of this pinpoint test for proper pin location.

Is the resistance less than 5 ohms?

Yes	No
GO to AB13.	GO to AB12.

AB12 CHECK INJECTOR FOR OPEN CIRCUIT

Key off.
Remove valve cover.
Disconnect injector connector.
Measure resistance on high side circuit from adapter tool to injector connector.
Measure resistance on low side circuit from adapter tool to injector connector.

Is each resistance less than 5 ohms?

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

AB13 CHECK FOR OPEN IN LOW SIDE CIRCUIT

Key off.
Disconnect IDM.
Measure resistance on injector low side circuit between the valve cover connector to the IDM.

Is resistance less than 5 ohms?

Yes	No
GO to AB14.	REPAIR open in low side circuit.

AB14 CHECK FOR OPEN IN HIGH SIDE CIRCUIT

Key off.
IDM disconnected.
Measure resistance between the suspect injector high side circuit on injector harness connector to IDM connector.

Is resistance less than 5 ohms?

Yes	No
Fault may be intermittent. GO to AB15.	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	No
ISOLATE open in circuit and REPAIR.	IDM internal failure. REPLACE IDM.

AB16 DIAGNOSTIC TROUBLE CODES (DTCs) 1291 AND 1292: CHECK FOR SHORT IN HIGH SIDE CIRCUIT

DTCs 1291 and 1292 indicate a ground short or short to battery positive exists on the high side circuit between the IDM and the injectors. The following table list the circuits to inspect while performing these pinpoint tests, based on the DTC retrieved during the KOEO test.

DTC	High Side	Bank
1291	1087 (O)	Right
1292	878 (PK/Y)	Left

Key off.
Disconnect IDM.
Using a DVOM and the flex tips supplied with the NGS Tester, measure resistance between the suspect high side circuit at the IDM harness connector to the battery negative post. Refer to injector illustration at beginning of this pinpoint test for proper pin location.

Is resistance greater than 10,000 ohms?

Yes	No
GO to AB18.	GO to AB17.

AB17 CHECK SHORT TO GROUND IN HIGH SIDE CIRCUIT

Key off.
IDM disconnected.
Disconnect both valve cover connectors on the bank with the code.
Measure resistance between the suspect high side circuit at the IDM connector to battery negative post.

Is resistance greater than 10,000 ohms?

Yes	No
GO to AB2.	REPAIR short to ground between IDM and injector valve cover connector.

AB18 CHECK SHORT TO POWER IN HIGH SIDE CIRCUIT

IDM disconnected.
Key on.
Measure resistance between the suspect high side circuit at the IDM connector to battery positive post, then to other high side circuit.

Are both resistance readings greater than 10,000 ohms?

Yes	No
Fault may be intermittent. GO to AB19.	REPAIR short to power on high side circuit.

AB19 CHECK FOR INTERMITTENT SHORT TO POWER IN HIGH SIDE CIRCUIT

IDM disconnected.
Key on.
Using a DVOM and the flex tips supplied with the NGS Tester, measure resistance between suspect high side circuit on the IDM connector to battery positive post, then to other high side circuit.
Grasp the harness close to the suspect injector harness connector. Wiggle, shake harness while working towards the IDM.

Do both resistance readings ever drop below 10,000 ohms?

Yes	No
ISOLATE short circuit and REPAIR. CLEAR DTC and RETEST.	IDM internal failure. REPLACE IDM.

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	No
GO to AB21.	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	No
Fault may be intermittent. GO to AB15.	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	No
REPLACE injector. RERUN Scan Tool Diagnostic Test.	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	No
REPLACE UVC harness.	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	No
Fault may be intermittent. GO to AB15.	REPAIR open in high side circuit.

AB25 DIAGNOSTIC TROUBLE CODES (DTCs) 0263, 0266, 0269, 0272, 0275, 0278, 0281 AND 0284: CYLINDER NON-CONTRIBUTING

Note: Each cylinder is tested in this order, 1-2-3-4-5-6-7-8, and does not always set a code, so you may have to run the test 3 or 4 times to verify that the noncontributing cylinder is constantly in the same hole.

A CCT code retrieved indicates that a cylinder was not contributing equally during the KOER Cylinder Contribution Self Test.

DTC	Cylinder	DTC	Cylinder
0263	1	0275	5
0266	2	0266	6
0269	3	0281	7
0272	4	0284	8

Possible causes:

Broken compression rings
Faulty injector assembly
Leaking or bent valves
Bent push rod
Broken rocker arm bolts
Bent connecting rod

Perform KOEO On-Demand Self Test, KOEO Injector Electrical Self Test, Retrieve Continuous. Refer to Scan Tool section for proper DTC retrieval procedure.

Were any DTCs retrieved?

Yes	No
REPAIR any concerns found. CLEAR DTCs and RETEST.	GO to AB26.

AB26 CYLINDER NON-CONTRIBUTING

Note: A/C must be off when running KOER Cylinder Contribution Self Test.

Perform steps 7a, 7b, 8, 10a, 10b, and 11 in the Performance Diagnostic Procedures section.

Were any problems found after running all of the above steps?

Yes	No
REPAIR any concerns found. CLEAR DTCs and RETEST.	If base engine diagnostic checks pass, REPLACE injector assembly. If base engine does not pass, REPAIR concern. CLEAR DTCs and RETEST.

AB27 DIAGNOSTIC TROUBLE CODE (DTC) 1297: BOTH INJECTOR HIGH SIDE CIRCUITS SHORTED TOGETHER

Key off.
Disconnect IDM.
Using a DVOM, measure resistance between both high side circuits at the IDM connector.

Is resistance greater than 10,000 ohms?

Yes	No
GO to AB28.	REPAIR short between both high side circuits.

AB28 CHECK FOR INTERMITTENT SHORT BETWEEN BOTH HIGH SIDE CIRCUITS

Key off.
Using a DVOM and the flex tips supplied with the NGS Tester, measure resistance between both high side circuits at the IDM connector, Pins 22 and 23.
Grasp the harness close to the IDM connector. Wiggle, shake harness while working towards the injectors.

Does resistance ever drop below 10,000 ohms?

Yes	No
ISOLATE short circuit and REPAIR.	IDM internal failure. REPLACE IDM.

AB29 DIAGNOSTIC TROUBLE CODES (DTCs) 1295 AND 1296: MULTIPLE CONCERNS

DTCs 1295 and 1296 indicate that more than one fault exists on the right or left bank. A short and open on both the low side and high side could exist on the bank with the DTC.

DTC	BANK
1295	Right Bank
1296	Left Bank

Check for short to ground:
Key off.
Disconnect IDM.
Measure the resistance of each injector circuit one by one to battery ground from the IDM harness connector.

Are all circuits greater than 10,000 ohms?

Yes	No
GO to AB30.	If low side short was found, GO to AB1 to find short, then RETURN to this step. If high side short was found, GO to AB16, then RETURN to this step.

AB30 CHECK FOR SHORT TO B+

Key off.
IDM disconnected.
Key on/engine off.
Measure the resistance of each injector circuit one by one to battery positive from the IDM harness connector.

Are all circuits greater than 10,000 ohms?

Yes	No
GO to AB31.	If low side short was found, GO to AB6, then RETURN to this step. If high side short was found, GO to AB16, then RETURN to this step.

AB31 CHECK FOR HIGH SIDE CIRCUIT SHORTED TOGETHER

Key off.
IDM disconnected.
Measure resistance between high side circuits from the IDM harness connector Pins 23 and 24.

Is resistance greater than 10,000 ohms?

Yes	No
GO to AB32.	REPAIR short between both high side circuits.

AB32 CHECK FOR OPEN CIRCUIT

Key off.
IDM disconnected.
Disconnect all four valve cover connectors on both banks.
Measure resistance between valve cover connector and IDM connector on all injector high side and low side circuits.

Are any circuits greater than 10,000 ohms?

Yes	No
REPAIR open in suspect circuit.	GO to AB33.

AB33 CHECK FOR OPEN UNDER VALVE COVER

Key off.
All four valve cover connectors disconnected.
Using Rotunda Glow Plug Injector Adapter 014-00935 or equivalent, measure resistance between high side and low side of every injector circuit through the valve cover.

Are any injector circuits greater than 5 ohms?

Yes	No
GO to AB12.	RECONNECT everything, CLEAR continuous DTCs and RERUN KOEO Injector Electrical Self Test and KOEO On Demand Self Test. If DTC 1295 or 1296 reappears, REPLACE IDM.