1994 Pontiac Trans Am cooling fans running and ses light on

Hi mvillebill,

Thank you for the donation.

When the SES light comes on and does not record any trouble codes, possible causes are :

1. Scan tester not compatible.
2. PCM memory power supply is missing. Check the fuses.
3. Faulty PCM.

One way to find out what went wrong to trigger the SES is to use a scanner to retrieve the freeze frame data. Plug in the scanner and test drive till the SES comes on and you can get the freeze frame data.

Alternative you can try to retrieve the trouble codes by manaul means.

RETRIEVING CODES (NON -SCAN)
NOTE: On models using a 12 -terminal DLC (previously referred to as the ALDL), if a wire is present at terminal "B", inserting a jumper wire into test and ground terminals of DLC with engine running will cause fuel injected vehicles to enter field service mode. Flashes of SERVICE ENGINE SOON light will not indicate codes if this is done. On models not using a 12 -terminal DLC or not having a wire present in terminal "B", codes must be retrieved using a hand -held scan tester.

1 . Turn ignition on. DO NOT start engine. SERVICE ENGINE SOON light should glow. Locate DLC attached to control module wiring harness. Most DLC's are located under dash on driver side of vehicle. Insert jumper wire from terminal "B" (diagnostic test terminal) to terminal "A" (ground) of DLC. See Fig. 1 .

2 . SERVICE ENGINE SOON light should begin to flash codes. Each code will be repeated 3 times. If codes are not flashed or SERVICE ENGINE SOON light does not glow, perform DIAGNOSTIC CIRCUIT CHECK in BASIC TESTING article in this section. To exit diagnostic mode, turn ignition off and remove jumper wire from DLC connector.

I will send some wiring diagrams under pdf format for you to understand the circuitry if you let me know your email.

The diagrams does not show up too well here.

What is the fuse that keeps blowing?

Hi Bill,

The Air Injection Pump is in the engine compartment, item # 9. The diagram shows the location but sorry, I could not find a better diagram in our database.

Unplug the air injection pump relay and test if the fuse still blows. If yes, then problem is caused by shorting between fuse and relay.

Fuse # 7 in underhood fuse box is the correct fuse and it only is used by the Air Injection Puump and its relay.

Here are the diagnostics for the problem if you don't have them.

CODE 29, SECONDARY AIR INJECTION
Ignition voltage is supplied voltage when ignition is on. PCM controls air pump relay by providing a ground through one of its Quad-Drivers Modules (QDM). When relay is actuated, terminal is grounded and its monitored voltage will be low. When an output is off, its terminal voltage will be high. Each QDM has a separate fault line to indicate presence of a current fault to control module central processor.

NOTE: Test numbers refer to numbers on diagnostic chart.

1 . Code 29 will set if the PCM detects the wrong voltage potential. Test will determine if relay can be controlled by PCM.

2 . This check can detect a partially shorted coil which would cause excessive current flow. Excessive current flow to a QDM will be detected as a fault and set a code.

3 . The remaining checks will identify a circuit problem that has caused an excessive current flow or inoperative relay.

Diagnostic Aids
Check related harness connectors, including PCM harness. Check for damaged or pushed out terminals.

The PCM side is not affected as voltage passes through the relay coil and directly grounding the the wire would only cause the relay to be activated.

The problem is either the wire from relay to pump or the pump itself. Unplug the pump connector and test with relay plugged, retest, if fuse does not blow, problem lies with the pump.

You can use a fused wire to apply voltage to terminal A of pump and grounding terminal C to see if the pump works.

You are welcomed and if you require futher assistance, we will always be here for you.

Thank you for using 2carpros.

Have a nice day.