How to tell if ecm pcm engine control module is bad

More than likely a broken wire, corroded connector or a chafed wire.

Yes, the ECM (Engine Control Module) and the PCM (Powertrain Control Module) are the same thing. Here is a picture of the ECM for a 1992 Cadillac DeVille Sedan: https://www.1aauto.com/images/items/items/KG/KG-1369/KG-1369-A.jpg.

1 photo from your service manual, (buy it?)
RF fender, drives seated perspectives.always.

Have your (alternator) Charging system tested ! .This is a computer controlled charging system .
The body control module (BCM) is a class 2 device. It communicates with the powertrain control module (PCM)/engine control module (ECM) and the instrument panel cluster (IPC) for electrical power management (EPM) operation. The BCM determines the output of the generator and sends the information to the PCM/ECM for control of the generator field control circuit. It monitors the generator field duty cycle signal circuit information sent from the PCM/ECM for control of the generator. It monitors a battery current sensor, the battery positive voltage circuit, and estimated battery temperature to determine battery state-of-charge (SOC). The BCM performs idle boost and load management operations.
Powertrain Control Module (PCM)/Engine Control Module (ECM) The PCM/ECM directly controls the generator field control circuit input to the generator. It monitors the generator's generator field duty cycle signal circuit and sends the information to the BCM. The PCM/ECM will override the BCM control of the generator when one of the following conditions is met:
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The engine cooling fans are on high speed.

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There is a high fuel demand.

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The calculated ambient air temperature is less that 0?°C (32?°F).

The gauge in the instrument cluster could be going bad ! maybe. Is that what your going by ? You need to have it hooked up to a scan tool ,not a code reader . It will tell what the ECT - engine coolant temperature sensor is reporting to the PCM - engine computer .The PCM turns on the cooling fans when the temp. reaches 262 degrees ! Are the cooling fans coming on ? Thermostat sticking ! Go to harbor freight an buy a Laser Temp Gun Infrared Thermometer , $30.00 . point it at the upper radiator hose an see what the actual temp is !
Engine Coolant Indicators
TEMP ?€¢
The instrument panel cluster (IPC) illuminates the TEMP indicator when the powertrain control module (PCM) determines that the coolant temperature is more than 128?°C (262?°F). The IPC receives a discrete input from the PCM requesting illumination.

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The IPC performs the display test at the start of each ignition cycle. The IPC illuminates the TEMP indicator.

Is the cooling system full of coolant ?
The instrument panel cluster (IPC) displays the engine coolant temperature as determined by the engine control module (ECM). The IPC receives a serial data message from the ECM indicating the engine coolant temperature. The IPC receives the coolant temperature information via serial data message from the body control module (BCM). The engine coolant temperature gage defaults to 60?°C (140?°F) or below if:
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The ECM detects a malfunction in the engine coolant temperature sensor circuit.

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The IPC detects a loss of serial data communications with the ECM.

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The IPC detects a loss of serial data communications with the BCM


Infrared Thermometer Gun Review

Engine Control Module (ECM) (LD8/L37)
Front left side of the engine compartment, inside the air cleaner housing.
Transmission Control Module (TCM) (LD8/L37)
At the left rear of the engine compartment, on the strut tower
They call it a PCM when TCM an ECM are all in one module. You have ECM an TCM

Error Code: P0130
Fault:
Oxygen Sensor (O2S) 1, Bank 1 - Circuit Malfunction
Possible Cause:
Malfunction Indicator Lamp (MIL) Triggered on first occurrence.
-Wiring harness.
-Oxygen sensor (O2S).
-Engine control module (ECM).

Error Code: P0505
Fault:
Idle Speed Control (ISC) System - Malfunction
Possible Cause:
-Wiring harness.
-Idle speed control (ISC) actuator/Idle air control valve (IAC) valve.
-Throttle motor.
-Throttle valve tight/sticking.
-Engine control module (ECM).

Error Code: P0100
Fault Location:
-Mass Air Flow (MAF) Sensor/Volume Air Flow (VAF) Sensor - Circuit --Malfunction
Possible Cause:
-Wiring harness.
-Mass air flow (MAF) sensor.
-Volume air flow (VAF) sensor.
-Engine control module (ECM).

Error Code: P1491
Fault:
Exhaust Gas Recirculation (EGR) Valve Insufficient Lift
Possible Cause:
-Wiring harness.
-EGR Valve.
-ECM

Error Code:P1607
Fault:
-Engine Control Module (ECM)/Powertrain Control Module (PCM)

Error Code: P0966
Location:
-Pressure Control (PC) Solenoid B - Circuit Low
Possible Cause:
-Wiring short to earth.
-Pressure control (PC) solenoid.
-Engine control module (ECM)/Powertrain control module -(PCM)/Transmission control module (TCM) .

P0621 Generator Lamp/L Terminal Circuit Malfunction,,The Engine Control Module (ECM) or Powertrain Control Module (PCM) uses the generator turn on signal circuit to control the load of the generator on the engine. A high side driver in the ECM/PCM applies a voltage to the voltage regulator. This signals the voltage regulator to turn the field circuit ON and OFF. The ECM/PCM monitors the state of the generator turn on signal circuit. The ECM/PCM should detect low voltage on generator turn on signal circuit when the ignition is ON and the engine is OFF, or when the charging system malfunctions. With the engine running, the ECM/PCM should detect high voltage on the generator turn on signal circuit. The ECM/PCM performs Ignition ON and RUN tests to determine the status of the generator turn on signal circuit.

P0203 - Injector Circuit Malfunction Cylinder 3

Powertrain Control Module (PCM) or Electronic Control Module (ECM) checks the injectors circuit resistance and monitors the voltage drop during normal operation. The PCM/ECM will trigger the P0203 code when the resistance or voltage drop at the injector #3 is out of specifications.

Causes:
- Open or shorted wiring harness to the injector #3
- Bad injector #3
- Bad PCM/ECM

Solutions:
- If damage, repair injector wire harness or connector
- Replace injector
- Replace PCM or ECM


P0204 - Injector Circuit Malfunction Cylinder 4

Same info as the P0203 DTC


P0300 - Random/Multiple Cylinder Misfire Detected

When a misfire occurs, engine speed will fluctuate. If the engine speed fluctuates enough to cause the crankshaft position (CKP) sensor (POS) signal to vary, Powertrain Control Module (PCM) or Electronic Control Module (ECM) can determine that a misfire is occurring.

Causes:
- Improper spark plug
- Insufficient compression
- Incorrect fuel pressure
- The injector circuit is open or shorted
- Fuel injectors may be faulty
- Intake air leak
- The ignition signal circuit is open or shorted

Solutions:
- Perform Injector Service
- Replace Spark Plugs
- Replace Injectors
- Replace Ignition Coils

The code P1698 is: No CCD messages from TCM. That means the communication between the Transmission Control Module and the Power Control Module is lost. Sometimes this happens when a PCM, or TCM is replaced without being flashed, a bad connection at the PCM, TCM, or a bad TCM. Hope this helps.