TEST 2: Circuits Shorted To Each Other

Circuits Shorted To Each Other. Bad PCM Causing MAP Sensor Code (1993, 1994 GM 4.3L, 5.0L, 5.7L) Circuits Shorted To Each Other. Bad PCM Causing MAP Sensor Code (1993, 1994 GM 4.3L, 5.0L, 5.7L) Circuits Shorted To Each Other. Bad PCM Causing MAP Sensor Code (1993, 1994 GM 4.3L, 5.0L, 5.7L)

So far, you have checked the continuity of the MAP sensor wires (between the PCM and the MAP sensor) in TEST 1.

The next step is to make sure that the MAP sensor wires are not shorted together. We can check this by testing for continuity between them with a multimeter in Ohms () mode.

In a normal system (one without problems), the MAP sensor wires are not connected to each other and so when checking for continuity... there should be none.

To be a bit more specific; This means that your multimeter should register OL (Open Loop) checking for continuity between them.

These are the test steps:

  1. 1

    Disconnect the battery from its negative cable. This will ensure that no circuit is ‘live’ with power before proceeding to the next step.

  2. 2

    Make sure the PCM is disconnected from its 2 connectors before proceeding to step 3.

  3. 3

    Check the continuity of MAP sensor connector terminals A and B with your multimeter in Ohms (). See image 1 of 3.

    Your multimeter should register OL (Open Loop) and NOT register continuity.

  4. 4

    Check the continuity of MAP sensor connector terminals A and C with your multimeter in Ohms (). See image 1 of 3.

    Your multimeter should register OL (Open Loop) and NOT register continuity.

  5. 5

    Check the continuity of MAP sensor connector terminals B and C with your multimeter in Ohms (). See image 3 of 3.

    Your multimeter should register OL (Open Loop) and NOT register continuity.

Let's take a look at what your test results mean:

CASE 1: None of the MAP sensor wires were shorted together. This is the correct and expected test result. Your next step is to make sure none of the MAP sensor wires are shorted to ground. For this test, go to: TEST 3: Checking For Shorts To Ground.

CASE 2: One or more of the MAP sensor wires were shorted together. Make sure that the PCM is disconnected from its two connectors.

If the PCM is unplugged from its two connectors then this test result tells you that you have a problem in the wiring since the multimeter should have NOT registered continuity.

Repairing the shorted MAP sensor wires will solve the MAP sensor problem and trouble codes.

TEST 3: Checking For Shorts To Ground

Checking For Shorts To Ground. Bad PCM Causing MAP Sensor Code (1993, 1994 GM 4.3L, 5.0L, 5.7L) Checking For Shorts To Ground. Bad PCM Causing MAP Sensor Code (1993, 1994 GM 4.3L, 5.0L, 5.7L) Checking For Shorts To Ground. Bad PCM Causing MAP Sensor Code (1993, 1994 GM 4.3L, 5.0L, 5.7L)

So far you have:

One: Confirmed all 3 MAP sensor wires have continuity between the PCM and MAP sensor (TEST 1).

Two: Confirmed that the MAP sensor wires are not shorted together (TEST 2).

In this test step, we'll make sure that the MAP sensor wires are not shorted to ground with a simple multimeter continuity test.

NOTE: The ground point (indicated in the test steps below) can be a good clean metal surface on the intake manifold or the engine since the battery negative terminal must remain disconnected from the battery negative post.

These are the test steps:

  1. 1

    The PCM, the battery negative terminal, and the automatic transmission must remain disconnected to accomplish the next test steps.

  2. 3

    Check the continuity of MAP sensor connector terminals A and ground with your multimeter in Ohms () mode. See image 1 of 3.

    Your multimeter should register OL (Open Loop) and NOT register continuity.

  3. 4

    Check the continuity of MAP sensor connector terminals B and ground with your multimeter in Ohms (). See image 1 of 3.

    Your multimeter should register OL (Open Loop) and NOT register continuity.

  4. 5

    Check the continuity of MAP sensor connector terminals C and ground with your multimeter in Ohms (). See image 3 of 3.

    Your multimeter should register OL (Open Loop) and NOT register continuity.

Let's take a look at what your test results mean:


CASE 1: None of the MAP sensor wires are shorted to ground. This is the correct and expected test result and it's looking like you just might have a bad PCM on your hands.

There's still one more set of tests you should do and it's to make sure that the PCM has power and ground. For these tests, go to: TEST 4: PCM Power And Ground Tests.

CASE 2: One or more of the MAP sensor wires were shorted to ground. Make sure that the PCM and the automatic transmission are disconnected from their connectors.

If the PCM and automatic transmission (4L60-E) are unplugged from their connectors, then this test result tells you that you have a problem in the wiring since the multimeter should have NOT registered continuity.

Repairing the shorted MAP sensor wires will solve the MAP sensor problem and trouble codes.