Test Procedure

WARNING: This page is about a different car, the 2006 Mercury Mariner and 2006 Ford Escape. However, it is still accessible from the selected car via links, so may be relevant.

TD1 DTC P0A18: VERIFY THAT THE HARD FAULT IS PRESENT

Record and clear all continuous memory DTCs.
Retrieve the PCM continuous memory DTCs.

Is DTC P0A18 present?

Yes	No
GO to TD2.	GO to TD7.

TD2 CHECK THE TMAC CIRCUIT FOR AN OPEN IN THE HARNESS

Key in OFF position.
PCM connector disconnected.
Transaxle Assembly-B connector disconnected.

Measure the resistance between:

( + ) PCM Connector, Harness Side	( - ) Transaxle Assembly-B Connector, Harness Side
TMAC - Pin T7	TMAC - Pin 4

Is the resistance less than 5 ohms?

Yes	No
GO to TD3.	REPAIR the open circuit.

TD3 CHECK THE TMAC CIRCUIT FOR A SHORT TO POWER IN THE HARNESS

Key ON, engine OFF.

Measure the voltage between:

( + ) PCM Connector, Harness Side	( - ) Vehicle Battery
TMAC - Pin T7	Negative terminal

Is the voltage less than 1 V?

Yes	No
Key in OFF position. GO to TD4.	Key in OFF position. REPAIR the short circuit to PWR.

TD4 CHECK THE TMAC CIRCUIT FOR A SHORT TO GROUND IN THE HARNESS

Measure the resistance between:

( + ) PCM Connector, Harness Side	( - ) Vehicle Battery
TMAC - Pin T7	Negative terminal

Is the resistance greater than 10K ohms?

Yes	No
GO to TD5.	REPAIR the short circuit to GND.

TD5 CHECK FOR THE TMAC CIRCUIT SHORTED TO SIGNALS IN THE SAME HARNESS

Measure the resistance between:

( + ) Transaxle Assembly-B Connector, Harness Side	( - ) Transaxle Assembly-B Connector, Harness Side
TMAC - Pin 4	ISDN2 - Pin 7
TMAC - Pin 4	GSDN - Pin 10
TMAC - Pin 4	CTO - Pin 1
TMAC - Pin 4	TGAC - Pin 9
TMAC - Pin 4	MSDN - Pin 5

Are the resistances greater than 10K ohms?

Yes	No
GO to TD6.	Key in OFF position. REPAIR the short circuit.

TD6 TMAC FUNCTIONAL TEST

PCM connector connected.
Transaxle Assembly-B connector connected.
Isolate the TMAC pin from the Transaxle-B connector.

Connect a 5 amp fused jumper wire between the following:

Point A Transaxle Assembly-B Connector, Harness Side	Point B Transaxle Assembly-B Connector, Harness Side
TMAC - Pin 4	TGAC - Pin 9

Key ON, engine running.

Does the engine start now?

Yes	No
Key in OFF position. INSTALL a new transaxle assembly.	Key in OFF position. GO to TD8.

TD7 CHECK THE TMAC CIRCUIT FOR AN INTERMITTENT CONCERN

Key ON, engine OFF.
Access the PCM and monitor the TMAC PID.
Carefully wiggle all accessible wiring and connectors associated with the circuit and look for a change in the PID state.

Is a concern present during the wiggle test?

Yes	No
Key in OFF position.	Key in OFF position.
REPAIR as necessary.	GO to Pinpoint Test Z .

TD8 CHECK FOR CORRECT PCM OPERATION

Disconnect all the PCM connectors.
Visually inspect for:
- pushed out pins.
- corrosion.
Connect all the PCM connectors and make sure they seat correctly.
Carry out the PCM self-test and verify the concern is still present.

Is the concern still present?

Yes	No
INSTALL a new PCM. REFER to FLASH ELECTRICALLY ERASABLE PROGRAMMABLE READ ONLY MEMORY (EEPROM) .	The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector.