I have a 91 D150 I need to pull some codes on but cannot find the DLC. Shop manual says its in the engine bay on the firewall but that's it. The only connectors I can find are off the bundle along the left fender that leads to the PCM past the TCC, starter and A/C relays. I know my truck uses the DRB II scan tool so maybe the data link connector is different than what I am used to seeing. Gettin' tired of looking at the damn MIL. Any help would be awesome!

 

ON-BOARD DIAGNOSTICS Dodge OBD1 Pre 96

1. Cycle the ignition key ON-OFF-ON-OFF-ON within 5 seconds. To cycle the ignition key ON means to turn it only as far as it takes to get the radio to come on. It does not mean to turn the engine on.

2. Count the number of times the "check engine" lamp on the instrument panel flashes on and off. The number of flashes represents the code. There is a slight pause between the flashes representing the first and second digits of the code. Longer pauses separate individual codes. For example, flash-flash-flash [pause] flash-flash represents the code 32.

A code of "55" represents end of error codes. If this is all you get then no error codes are stored in the computer. This is the normal condition

CODE Description of Trouble Code
11 Timing belt skipped 1 tooth or more from initial learned value, Intermittent loss of either camshaft or crankshaft position sensor, No crank reference signal detected during engine cranking
12 Direct battery input to PCM was disconnected within the last 50 key-on cycles (normal)
13 No change in MAP from start to run
14 MAP sensor voltage too low
15 No vehicle speed sensor signal
17 Closed loop temp not reached or engine cold too long
21 02s sensor problem (oxygen sensor), upstream or down stream
22 Engine coolant temp sensor out of range
23 Intake air temp sensor out of range
24 Throttle Position sensor out of range
25 Idle air control motor circuits, target idle not reached (+/- 200),vacuum leak found
27 Injector control circuit
31 Evap purge flow monitor failure or evap solenoid circuit
32 EGR system failure
33 A/C clutch relay circuit
34 Speed control Solenoid circuits
35 Rad Fan control relay circuit
37 Torque converter clutch solenoid CKT or park/neutral switch failure
41 Generator field not switching properly
42 Fuel pump relay control ckt, Auto shutdown relay control ckt, No ASD relay output voltage at PCM, Fuel level sending unit volts out of range, Fuel level unit No change over miles
43 Multiple/ single cylinder misfire
44 Battery temp sensor volts out of range
46 Charging system voltage too low
51 Fuel system lean
52 Fuel system rich
53 Internal control failure
54 No Cam signal at PCM
55 End of error messages (If you get this only, no errors were found)
62 PCM failure SRI mile not stored
63 PCM Failure EEPROM write denied
64 Catalytic Converter Efficiency Failure
65 Power steering switch failure

 

it should be around your starter and a/c relays.

 

Great, thank you.