Monthly Archives: March 2016

No luck on the replacement ECM

I replaced the ECM with a remanufactured one. Symptoms remain unchanged.

At this point, I suspect the problem is inside the wiring harness.

I am going to take the truck to By The Book Diesel in Albuquerque next week and let them have a look at it.

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Replacement ECM for the Ram

On Saturday, I performed the  P1652-J1850 Short to Ground test procedure from the service manual (p. 205):

p1652-short-to-ground

This involves removing the inner fender, disconnecting the 50-pin (rearmost, closest to the driver) Engine Control Module (ECM) connector, and measuring the resistance between battery negative and pin 28 in the harness connector, which connects to a violet-with-yellow-stripe wire that connects the ECM to the J1850 PCI bus.

The test determines whether there is a short to ground in the wiring harness itself. If the resistance is less than ten ohms, then there is a short in the wiring harness (or in one of the modules connected to the PCI bus). If, however, the resistance is 10 or more ohms, then the problem isn’t in the wiring harness or any of the modules, and there’s only one other place where the short can be occurring — in the ECM itself.

Resistance between ground and harness pin 28 was approximately 1.2 kOhm, very high. Not at all likely there’s a short downstream of the ECM.

So it was time to replace the ECM. Problem is, although there are quite a few places that sell reman’d Cummins ECMs, many (most?) of them are disreputable. I managed to find one, Reman Auto Electronics in Lewisberry, PA, which has a good reputation and a good price — $800 for a remanned 03 ECM. They called me this morning to get the VIN, transmission type, emissions type and the code off the valve cover so they can flash the computer. It should be here in a week.

For reference, here are pinouts of the two ECM connectors:

First, the front (furthest from driver), 60-pin connector:

ecm1

ENGINE CONTROL MODULE C1 (DIESEL) – 60 WAY

CAV CIRCUIT FUNCTION
1
2
3
4 D1 18VT/BR CCD BUS (+)
5 D2 18WT/BK CCD BUS (-)
6 K65 18OR/RD FUEL PUMP SUPPLY
7 K20 18DG GENERATOR FIELD CONTROL
8
9
10
11
12 K102 18PK/BK FUEL PRESSURE SENSOR SIGNAL
13
14 K23 18BR/WT (LATE BUILD M/T) APPS SIGNAL NO. 1
15 K21 18BK/RD INTAKE AIR TEMPERATURE SENSOR SIGNAL
16 K29 18WT/BR (LATE BUILD M/T) APPS SIGNAL NO. 2
17 K2 18TN/BK ENGINE COOLANT TEMPERATURE SENSOR SIGNAL
18
19 K31 18BR FUEL PUMP RELAY CONTROL
20
21
22 G17 18WT/TN CKP SIGNAL
23 K104 18RD/WT SENSOR GROUND
24 K53 18DB/RD (EARLY BUILD) CMP SIGNAL
24 K53 18DB (LATE BUILD) CMP SIGNAL
25 Y501 18DB/YL 5 VOLT SUPPLY
26 C18 18DB A/C PRESSURE SIGNAL
27 K6 18VT/WT 5 VOLT SUPPLY
28
29 Y502 18DG/YL INLET AIR TEMPERATURE/PRESSURE RETURN
30 K11 16WT/DB FUEL INJECTOR NO. 1 DRIVER
31 G20 18VT/YL WATER IN FUEL SENSOR SIGNAL
32 K55 18LB/WT SENSOR RETURN
33 K56 18LG/OR (LATE BUILD M/T) APPS SENSOR RETURN NO. 1
34 K49 18VT/BK APPS IDLE SWITCH
35
36 K14 16RD/WT FUEL INJECTOR NO. 4 DRIVER
37
38
39
40 K13 16TN FUEL INJECTOR NO. 3 DRIVER
41
42 K852 18BR/VT (LATE BUILD M/T) 5 VOLT SUPPLY
43 K9 18LB 5 VOLT SUPPLY
44 K101 18WT NOT IDLE SWITCH
45 K62 18BK/OR LIFT PUMP FEED
46 K58 16BR/DB FUEL INJECTOR NO. 6 DRIVER
47
48
49
50 K12 16YL/WT FUEL INJECTOR NO. 2 DRIVER
51
52 K167 18BR/YL SENSOR GROUND
53 G910 18VT/RD FUEL PRESSURE SENSOR SIGNAL RETURN
54 K72 18DG/OR 5 VOLT SUPPLY
55
56 K38 16GY FUEL INJECTOR NO. 5 DRIVER
57 K92 16TN/PK COMMON INJECTOR DRIVER
58
59 K91 16TN/RD COMMON INJECTOR DRIVER
60

 

Next, the rear (closest to driver) 50-pin connector:

ecm2

ENGINE CONTROL MODULE C2 (DIESEL) – 50 WAY

CAV CIRCUIT FUNCTION
1 K22 18DR/DB THROTTLE POSITION SENSOR SIGNAL
2 K24 18WT/DG CRANKSHAFT POSITION SENSOR SIGNAL
3 K69 18 BR/LB INJECTOR CONTROL SIGNAL NO.1
4
5 K154 18GY INTAKE AIR HEATER RELAY NO. 2
6 K152 18WT INTAKE AIR HEATER RELAY NO. 1
7
8
9
10 Y5 18OR FAN SPEED SENSOR
11 G7 18WT/OR VEHICLE SPEED SIGNAL
12 G60 18GY/YL ENGINE OIL PRESSURE SWITCH SENSE
13
14
15
16 D21 18PK SCI TRANSMIT
17
18
19 D20 18LG SCI RECEIVE
20 A140 16DG/WT FUSED B(+)
21 Z816 16BK/TN GROUND
22
23 Y3 18WT
24 K4 18BK/LB SENSOR GROUND 1
25
26 G8 18 LB/BK FUEL LEVEL SENSOR SIGNAL
27 K77 18 BR/WT TRANSFER CASE POSITION SENSOR INPUT
28 D25 18VT/YL PCI BUS
29
30 A140 16DG/WT FUSED B(+)
31
32 Y135 18LG/BK FUSED IGNITION SWITCH OUTPUT (RUN-START)
33
34
35 K68 18BR/LG INLET AIR PRESSURE SENSE
36 V32 18YL/RD SPEED CONTROL SUPPLY
37 K29 18WT/PK BRAKE SWITCH SENSE
38
39
40 A140 16DG/WT FUSED B(+)
41 C13 18DB/OR A/C CLUTCH RELAY CONTROL
42
43 Y1 18LG FAN SPEED CONTROL
44
45
46 V37 18RD/YL S/C SWITCH SIGNAL
47 K118 18PK/YL BATTERY TEMPERATURE SENSOR SIGNAL
48 K400 18BR/VT ACCELERATOR PEDAL POSITION SENSOR RETURN NO. 2
49 Z816 16BK/TN GROUND
50 Z816 16BK/TN GROUND