Diagnostic Strategy. Diagnosis and Testing

Overview

The diagnostic process for each transmission concern will vary depending on the symptoms and condition of the vehicle. The following is an effective method for gathering as much information as possible about the concern before performing repairs or removing the transmission from the vehicle for disassembly and further inspection. Intermittent concerns and concerns that result in default or limp-home operation may be difficult to diagnose.

Automatic Transmission Diagnosis

Many transmission faults result in one or more Diagnostic Trouble Codes (DTCs) being stored in the Powertrain Control Module (PCM). In some cases, a group of DTCs may indicate a specific fault. The transmission may operate only in default or fail-safe modes when certain DTCs are set.

Begin diagnosis by performing a PCM self-test: KOEO and CMDTC. and KOER and CMDTC. Record all diagnostic trouble codes (DTCs) and associated freeze frame data. Clear the diagnostic trouble codes (DTCs) after recording the information.

Preliminary Inspection

The preliminary inspection will include:

1. 1
   Locate obvious causes of concern by performing a visual inspection under the hood and under the vehicle.
2. 2
   Adjust the selector lever linkage (if equipped).
3. 3
   Collect a fluid sample.

PID Monitor / Road Test Recording

Using the DTCs and freeze frame data as a guide, prepare the scan tool to record the event. Select the transmission Parameter Identifications (PIDs) related to the concern, as well as the PIDs for general automatic transmission operation. Because you may only get one or two chances to duplicate the concern, it is better to record more data. If possible, set the data logger to start recording automatically when a PID reaches a specified value. For example, you may want recording to start 6 seconds before the fault PID changes from "No Fault" to "Fault".

The PCM/TCM may set a DTC after the first occurrence of a fault. Some DTCs may require up to 5 consecutive repeats before being set. Operate the vehicle under conditions similar to the freeze frame data, if possible. If freeze frame data is not available, perform this road test:

• Drive the vehicle normally for 1–3 minutes to warm the fluid.
• From a standstill, accelerate the vehicle to 80 km/h. Shifts should occur at approximately 2000 rpm. Remain in 6th gear for 30 seconds or until the TCC applies. Repeat this two times.
• From a standstill, accelerate the vehicle to 80 km/h. Shifts should occur at approximately 3000 rpm. Remain in 6th gear for 30 seconds or until the TCC applies. Repeat this two times.

After the road test, review the recording and check for newly set diagnostic trouble codes (DTCs). Electrical DTCs are diagnosed using pinpoint tests. Hydraulic, mechanical and performance DTCs are diagnosed by component testing. Use the DTC chart for detailed diagnosis:
Refer to: Automatic Transmission - 1.5 L EcoBoost (118 kW/160 L PS) - I4 (307-01A Automatic Transmission - 6-Speed Automatic Transmission - 6F35, Diagnosis and Testing).
Refer to: Automatic Transmission - 2 L EcoBoost (184 kW/250 L PS) - MI4 (307-01A Automatic Transmission - 6-Speed Automatic Transmission - 6F35, Diagnosis and Testing).
Refer to: Automatic Transmission - 2.5 L Duratec (125 kW/170 L PS) (307-01A Automatic Transmission - 6-Speed Automatic Transmission - 6F35, Diagnosis and Testing).
Refer to: Automatic Transmission - 2.7 L EcoBoost (238 kW/324 L PS) (307-01B Automatic Transmission - 6-Speed Automatic Transmission - 6F50/6F55, Diagnosis and Testing).

If no diagnostic trouble codes (DTCs) are set, use the gathered data, the clutch application chart and the solenoid application chart to determine the transmission systems suspected of causing the concern. Use component testing to diagnose each suspect system.

Pinpoint Tests

Pinpoint tests are divided by component or system. Each test is a series of circuit checks to verify the integrity of the wiring harness between the PCM/TCM and the solenoid or sensor.

Component Tests

Component tests are divided by system. Each test lists the possible symptoms the system may exhibit. For each symptom, a list of components that may cause the symptom is provided. Components are listed in order from least likely to most likely to be the cause.

Perform Repair

An automatic transmission contains more than 400 individual components. All of these components must be in good working condition. Many repairs are relatively simple. In this repair, you will:

• Clean and inspect all removed parts.
• Attempt to determine the root cause of the failure.
• Identify and repair/replace any related damaged parts.
• Thoroughly document the results on the repair order.

In the event of clutch failure, when the transmission fluid is heavily contaminated with friction material, the transmission must be completely overhauled. The overhaul requires complete disassembly and cleaning of the transmission. All seals and gaskets (except the reusable oil pan gasket) must be replaced.

Complete Overhaul

After reassembling the transmission, complete the following steps before returning the vehicle to the customer.

• Initial Transmission Fluid Fill: this can be performed before the transmission is installed in the vehicle.
• Clear Adaptive Tables: required after a complete overhaul and when the solenoid body is replaced.
• Reset Misfire Monitor: required whenever the transmission has been removed.
• Road Test until the transmission fluid reaches Operating Temperature. This is necessary to ensure the transmission fluid cooler is filled with transmission fluid.
• Perform Adaptive Drive Cycle: required if the adaptive tables have been cleared.
• Set the transmission fluid level: the transmission fluid is now at the correct temperature and the transmission fluid cooler has been purged of air.
• Verify the repair has corrected the concern: this is also known as the post-repair road test.