Diagnostic Aids
WARNING: This page is about a different car, the 2004 Pontiac Grand Prix. However, it is still accessible from the selected car via links, so may be relevant.
- DTC P1518 sets if the battery voltage is low or the PCM is replaced or reflashed. If the customer's concern is slow cranking, or if the engine is not cranking because the battery voltage is low, ignore DTC P1518. Clear any DTCs from memory that may have set from the low battery voltage condition.
- If the condition is intermittent, refer to Intermittent Conditions .
DTC P1518
| Step | Action | Values | Yes | No |
|---|---|---|---|---|
| Schematic Reference: Engine Controls Schematics Connector End View Reference: Powertrain Control Module (PCM) Connector End Views and Engine Controls Connector End Views |
||||
| 1 | Did you perform the Diagnostic System Check-Engine Controls? | - | Go to Step 2 | Go to Diagnostic System Check - Engine Controls |
| 2 |
|
0 V | Go to Step 3 | Go to Diagnostic Aids |
| 3 |
|
0 V | Go to Step 4 | Go to Step 10 |
| 4 |
|
B+ | Go to Step 5 | Go to Step 12 |
| 5 |
|
5ohm | Go to Step 6 | Go to Step 13 |
| 6 |
|
2-5 V | Go to Step 14 | Go to Step 7 |
| 7 | Does the voltage measure more than the specified value? | 5 V | Go to Step 11 | Go to Step 8 |
| 8 | Does the voltage measure less than the specified value? | 5 V | Go to Step 9 | - |
| 9 | Test for an open or for a short to ground in the serial data circuit. Refer to Circuit Testing
and Wiring Repairs
in Wiring Systems. Did you find and correct the conditions? |
- | Go to Step 19 | Go to Step 17 |
| 10 | Repair the short to battery voltage in the ignition 1 voltage circuit. Refer to Wiring Repairs
in Wiring Systems. Did you complete the repair? |
- | Go to Step 19 | - |
| 11 | Test for a short to voltage on the TAC module serial data circuit. Refer to Circuit Testing
and Wiring Repairs
in Wiring Systems. Did you find and correct the conditions? |
- | Go to Step 19 | Go to Step 18 |
| 12 | Repair the open or short to ground in the ignition 1 voltage circuit. Refer to Wiring Repairs
in Wiring Systems. Did you complete the repair? |
- | Go to Step 19 | - |
| 13 | Repair the open or high resistance in the TAC module ground circuit. Refer to Wiring Repairs
in Wiring Systems. Did you complete the repair? |
- | Go to Step 19 | - |
| 14 | Test the ETC ignition 1 voltage circuit for the high resistance. Refer to Circuit Testing
and Wiring Repairs
in Wiring Systems. Did you find and correct the condition? |
- | Go to Step 19 | Go to Step 15 |
| 15 | Test for an intermittent and for a poor connection at the throttle body. Refer to Testing for Intermittent Conditions and Poor Connections
and Connector Repairs
in Wiring Systems. Did you find and correct the condition? |
- | Go to Step 19 | Go to Step 16 |
| 16 | Replace the throttle body assembly. Refer to Throttle Body Assembly Replacement (L26)
or Throttle Body Assembly Replacement (L32)
. Did you complete the replacement? |
- | Go to Step 19 | - |
| 17 | Test for an intermittent and for a poor connection at the powertrain control module (PCM). Refer to Testing for Intermittent Conditions and Poor Connections
and Connector Repairs
in Wiring Systems. Did you find and correct the condition? |
- | Go to Step 19 | Go to Step 18 |
| 18 | Replace the PCM. Refer to Powertrain Control Module (PCM) Replacement
. Did you complete the replacement? |
- | Go to Step 19 | - |
| 19 |
|
- | Go to Step 2 | Go to Step 20 |
| 20 |
IMPORTANT:
Be aware that repairing 1 individual condition may correct more than 1 DTC. Observe the Capture Info with a scan tool.Are there any DTCs that have not been diagnosed? |
- | Go to Diagnostic Trouble Code (DTC) List | System OK |