Nautilus

iTrader: (15)

On the drive down to SC a month ago my car started throwing some codes.... and the ses light has been on since then... can anyone tell me what causes these codes?

P0420 H C: TWC System Low Efficiency Bank 1-A

P0430 H C: TWC System Low Efficiency Bank 2-A

P1518 H: PCM to TAC Module Serial Data Circuit -

I know the H is for history code and I thought the C is for a "current" code... but I cleared them and have driven about 100 miles last night and the codes haven't come back... I just want to know what can cause those codes?

Noyzee

iTrader: (37)

lak of Nitrous will cause that

Nautilus

iTrader: (15)

I thought you were going to tell me the color caused them

Noyzee

iTrader: (37)

well, that to

Humvee z28

i know the 420/430 codes are catalyst inefficiency codes.... just have them permeantly erased from the PCM. as for the other one i do now know

SteveDoten@ARH

exactly, 420/30 is common if not standard w/ LT's, the tac code is often seen on 97/8's

badpewter-z

iTrader: (4)

PO420 and PO430 are o2 sensor codes

PO1518 is a tac to pcm code

DTC P1518
Table 1: DTC P1518 - PCM to TAC Module Serial Data Circuit

Circuit Description
The throttle actuator control (TAC) module and the powertrain control module (PCM) communicate via a dedicated serial data circuit. This serial data circuit is separate from any other serial data circuit on the vehicle. Accurate transmitting and receiving of serial data requires not only good circuit integrity, but also adequate system voltage. This diagnostic monitors the accuracy of the serial data transmitted between the TAC module and the PCM. If the PCM detects a loss of data or invalid data, this DTC sets.

Conditions for Running the DTC
The ignition switch is in the crank or the run position.
The ignition voltage is greater than 5.23 volts.
Conditions for Setting the DTC
Invalid or missing serial data messages are detected for a predetermined amount of time.
All of the above conditions met for less than 1 second.
Action Taken When the DTC Sets
The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.
The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame and/or the Failure Records.
The control module commands the TAC system to operate in the Reduced Engine Power mode.
A message center or an indicator displays Reduced Engine Power.
Under certain conditions the control module commands the engine OFF.
Conditions for Clearing the MIL/DTC
• The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.

• A current DTC, Last Test Failed, clears when the diagnostic runs and passes.

• A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.

• Clear the MIL and the DTC with a scan tool.

Diagnostic Aids
DTC P1518 sets if the battery voltage is low. If the customer's concern is slow cranking or no crank because battery voltage is low, ignore DTC P1518. Clear any DTCs that may have set from the low battery voltage condition from the memory.
DTC P1518 sets when there is a short to B+ on the TAC module ground circuit. Inspect the fuses for the circuits that are in the TAC module harness, such as the cruise, or the brake. An inspection of the fuses may lead you to the circuit that is shorted to the TAC module ground circuit.
DTC P1518 sets if the TAC module ignition feed circuit is shorted to a B+ supply circuit. The TAC module stays powered-up when the ignition switch is turned off. When the ignition switch is turned on, the TAC module is powered-up before the PCM. DTC P1518 sets because no communication is detected by the TAC module from the PCM. Inspect related circuits for being shorted to a B+ supply circuit.
Inspect the TAC module power and ground circuits and the TAC module/PCM serial data circuits for intermittent connections.
Inspect the TAC module connectors for signs of water intrusion. When water intrusion occurs, multiple DTCs could be set with no DTC circuit or component conditions found during diagnostic testing.
When the TAC module detects a problem within the TAC system, more than 1 TAC system related DTC may set. This is due to the many redundant tests that run continuously on this system. Locating and repairing 1 individual problem may correct more than 1 DTC. Keep this in mind when reviewing captured DTC info.

Nautilus

iTrader: (15)

Cool, thanks for the info....

BrentC5

Hey Tim, If you do a search on the forum for DTC codes all the codes will show up. Good thing to printout beacause the vette throws codes all the time. my man badpewter is right it's the 02 sensors. H is history and c is current. Never heard of the other one and i dont want to know. If you dont know how to reset let me know with manual diagnostics let me know.

Slowhawk

iTrader: (12)

420 and 430 have to be deleted if the tuning delete's the rear 02's.

It's a Vette thing.

Nautilus

iTrader: (15)

Thats how I figured it out... did a search and came up with these directions... http://www.z06vette.com/ipc.txt
I've deleted the codes using the manual diagnostics... but I'm assuming thats only temporary and at some point they'll pop back up.


Thanks, I'm assuming these can be permanently deleted with a tune?

badpewter-z

iTrader: (4)

any code can be deleted permently

Humvee z28

had the same issue with my camaro, and now they are permeantly gone

BrentC5

Just do what I do, start it up in the morning and while the motor is warming up delete the codes. It takes 2 sec. Hell I've even got a radio code. No fooling.

Nautilus

iTrader: (15)

Haha, yeah I also have codes for some power module in my driver side door...

BrentC5

The vette is code happy.