GM Service Manual Online
For 1990-2009 cars only

Step

Action

Value(s)

Yes

No

1

Has the vehicle been inspected for Diagnostic Trouble Codes (DTCs)?

--

Go to Step 2

Go to Engine Controls

2

  1. Disconnect the Powertrain Control Module (PCM) connector C1.
  2. Turn the ignition switch to the RUN position.

Does the fuel gauge read FULL?

--

Go to Step 3

Go to Step 4

3

  1. Turn the ignition switch to the OFF position.
  2. Leave the PCM connector C1 disconnected.
  3. Connect a fused jumper (3 A), from the PCM connector C1 terminal 3 to ground.
  4. Turn the ignition to the RUN position.

Does the fuel gauge read EMPTY?

--

Go to Step 7

Go to Step 4

4

  1. Remove the instrument cluster.
  2. Use a DMM in order to probe for continuity between the PCM connector C1 terminal 3 and the instrument cluster connector C! terminal D.

Is CKT 55 continuous between the PCM connector C1 terminal 3 and the instrument cluster connector C1 terminal D?

--

Go to Step 6

Go to Step 5

5

  1. Repair the open, the short to ground, or the short to battery power in CKT 55.
  2. Inspect the system.

Is the symptom still present?

--

Go to Step 6

System OK

6

  1. Replace the instrument cluster. Refer to Instrument Cluster Replacement .
  2. Inspect the system.

Is the symptom still present?

--

Go to Step 7

System OK

7

  1. Turn the ignition switch to the OFF position.
  2. Disconnect the PCM connector C2.
  3. Disconnect connector C405.
  4. Connect a (3A) fused jumper between C405 terminal 3D and ground.
  5. Use a DMM in order to probe for continuity between the PCM connector C2 terminal 69 and ground.

Is the CKT 30 continuous between connector C405 terminal F and the PCM connector C2 terminal 69?

--

Go to Step 8

Go to Step 9

8

  • Disconnect the fused jumper (3A) between C405 terminal F and ground.The DMM should remain connected between the PCM connector C2 terminal 69 and ground.

Is CKT 30 shorted to ground?

--

Go to Step 9

Go to Step 10

9

  1. Repair the open, the excessive resistance, or the short to ground in CKT 1589 between the PCM connector C2 terminal 69 and the fuel level sending unit connector.
  2. Inspect the system.

Is the symptom still present?

--

Go to Step 10

System OK

10

  1. Reconnect the PCM connectors C1 and C2.
  2. Connect the J 33431-C between C405 terminal F and ground.
  3. If J 33431-C is unavailable, use a resistor of equal value.

  4. Turn the ignition switch to the RUN position.
  5. Vary the J 33431-C resistance from 40 ohms to 250 ohms.

As the resistance values change, does the fuel gauge indicator change values approximately equal to those in the table following this diagnosis?

--

Go to Step 11

Go to Step 14

11

  1. Turn the ignition switch to the OFF position.
  2. Disconnect the PCM connector C1.
  3. Inspect for a poor connection or an open in CKT 452 between the PCM connector C2 terminal 35 and the connector C405 terminal 3B.

Does a poor connection or an open in CKT 452 between the PCM connector C1 terminal 35 and the connector C405 terminal 3B exist?

--

Go to Step 12

Go to Step 13

12

  1. Repair CKT 452 between the PCM connector C2 terminal 35 and the connector C405 terminal B for an open or an excessive.
  2. Inspect the system.

Is the symptom still present?

--

Go to Step 13

System OK

13

  1. Inspect the fuel tank sending unit connector for poor terminal connections.
  2. Inspect the float for any obstructions or damage.
  3. Inspect the system.

Is the symptom still present?

--

Go to Step 14

System OK

14

  1. Replace the powertrain control module. Refer to Engine Controls.
  2. Inspect the system.

Is the symptom still present?

--

--

System OK

Sender Resistance

Approximate Fuel Level

245 ohms

FULL

180 ohms

¾

160 ohms

½

100 ohms

¼

42 ohms

EMPTY