Issue Summary:
- Mitsubishi’s onboard computer system presents transmission-related “P” codes that are misleading, causing needless, unproductive diagnostic routines and repairs.
- The A4AF3/A4BF2 transaxles used in Hyundai Accent, Elantra and Tiburon since model year 2000 are nearly identical to the A4AF1/A4AF2 units they replaced but have some differences.
- Solenoid locations, connector-pin ID and bench checks are provided for Mitsubishi F4A-41/42/51 series transaxles.
- For the 1995-98 Mitsubishi Eclipse non-turbo 2.0-liter with the Chrysler A604 transaxle, you gain diagnostic access through the Chrysler partition of the Snap-on Scanner’s Domestic Primary Cartridge.
Mitsubishi’s onboard computer system presents transmission-related “P” codes that are misleading, causing needless, unproductive diagnostic routines and repairs.
A simplified example that will serve as some type of reasonable explanation would be to look at code P1750. This code is defined to mean that any of the solenoid circuits are either open or shorted. If these solenoids and their respective wiring to the ECM prove good, then the ECM is defective.
Now if you looked at the two-digit transmission-code list you would see that codes 41 to 48 are individual codes for each type of circuit failure for each of the solenoids in the transmission. Yet code 49 is not an electrical fault code but rather it represents a mechanical failure of the converter clutch. It is this code that got brought over together with codes 41 to 48 on the ECM’s lookup table to be represented by the “P” code 1750.
If you have ever experienced installing into a vehicle a transmission with an incorrect gear ratio, you also know that the result often produces a TCC slip code that will not go away. So here is an example of a “P” code that could mislead a technician into changing solenoids, replacing wiring or even replacing the ECM when all along it was either some type of hydraulic/mechanical failure of the converter clutch, a slipping transmission or an incorrect transmission was installed.
One important additional note: P0700 has been designated to mean many different possibilities. Definitions vary from Relay Stuck Off to Defective Computer. What this code really means is that the ECM/PCM has received information that the TCM has stored a code. It is simply an MIL request light directing the technician to obtain two-digit transmission codes.
Never rely on OBD-II codes for the transmission. Always use an analog voltmeter and acquire the two-digit transmission codes for greater diagnostic accuracy.
Use Figure 1 to see which terminals to connect the analog meter to for any year, make or model of vehicle with a KM/F4-style unit.
Use Figure 2 for the appropriate code list that matches the generation of computer on the vehicle.
To determine which generation the vehicle’s computer is, use Figure 3 to locate the computer and Figure 4 to identify the computer.
Since model year 2000, Hyundai has been using a new transaxle in the Accent, Elantra and Tiburon. It is the A4AF3 for use with 1.5-liter engines and the A4BF2 for use with 2.0-liter engines. These transaxles are almost identical to the A4AF1 and A4AF2, but with several major exceptions. The A4AF1 and A4AF2, as well as the new A4AF3 and A4BF2, are almost identical to the KM series except that they are “backward.”
The big change is the addition of two solenoids (see Figure 5 for solenoid locations), a handful of valves and an accumulator for the forward (rear) clutch. One of the solenoids is pressure-control solenoid B (PCSB).
The EPC is now referred to as pressure-control solenoid A (PCSA). PCSB now directly controls the application of the direct (front) clutch/servo release circuit. The other new solenoid is shift-control solenoid C (SCSC). In first or second gear, pressure to the servo-apply side is controlled by PCSA as it always has been. For third and fourth gears SCSC causes full line pressure to remain on the apply side of the servo all the time, including during the shift. This gives PCSB far greater control over the direct-clutch apply timing. This should take care of 2-3 flares, 4-3 bumps, delayed reverse engagement and other timing issues related to the direct clutch. The new valves are only to support the new solenoid scheme. They are the failsafe valve, the control-switch valve and the high/low-pressure valve. The checkballs remain the same as in other KM-style units.
With the addition of the new solenoids come changes to the diagnostic trouble codes. Although not as generalized as code P1750 (solenoid-pack fault), the new codes do not specify whether a solenoid circuit is open or shorted. It does specify which solenoid, though. P0760 indicates a fault in the SCSC circuit, and P0765 is for the PCSB. Both will cause the MIL to light and a failsafe condition. See Figure 6 for a complete code list.
The pin on the diagnostic connector used to manually retrieve codes with an analog voltmeter has changed to 1 (see Figure 7).
In addition to the code changes, changes also were made to the pin-outs to accommodate the two new wires. The case connector is now six pins (see Figure 8).
The computer appears identical to a fourth-generation KM computer, but the pin assignments have changed (see Figure 9).
One other note: The A4AF3 and A4BF2 do still have creep mode, but there is no longer a separate switch to control it. Creep mode is now controlled by the computer via the TPS and VSS inputs. Further, the TPS signal is now routed through the ECM rather than being split to both the TCM and the ECM.
Figure 10 shows the locations of the solenoids and the ATF temperature sensor.
Figure 11 identifies the terminals in the case connector.
Figure 12 provides resistance values for the solenoids and ATF temperature sensor.
For the 1995-98 Mitsubishi Eclipse non-turbo 2.0-liter with the Chrysler A604 transaxle, you gain access through the Chrysler partition of the Domestic Primary Cartridge. You must use the MITSU-1 adapter that connects to both the Mitsubishi and OBD-II diagnostic connectors using personality key number 7 (see Figure 13).
If you are using a ’97 or ’98 Primary Cartridge, enter the following vehicle identification numbers:
- 10th digit – Use the vehicle’s 10th VIN digit
- 5th digit – “U”
For those who have the ’99 Primary Cartridge, use the following numbers:
- 10th digit – Use the vehicle’s 10th VIN digit
- 2nd digit – E
- 3rd digit – 3
- 8th digit – Y
- 5th digit – U
March 2004 Issue
Volume 21, No. 3
- Mitsubishi Code Retrieval: Misleading ‘P’ Codes
- Hyundai A4AF3/A4BF2: Preliminary Information
- Mitsubishi F4A-41/42/51 Series Transaxles: Solenoid Locations, Connector-Pin ID and Bench Checks
- Mitsubishi/DaimlerChrysler: Snap-on Scanner Access